linux/kernel/trace/ring_buffer.c
Petr Pavlu 09661f75e7 ring-buffer: Fix reader locking when changing the sub buffer order
The function ring_buffer_subbuf_order_set() updates each
ring_buffer_per_cpu and installs new sub buffers that match the requested
page order. This operation may be invoked concurrently with readers that
rely on some of the modified data, such as the head bit (RB_PAGE_HEAD), or
the ring_buffer_per_cpu.pages and reader_page pointers. However, no
exclusive access is acquired by ring_buffer_subbuf_order_set(). Modifying
the mentioned data while a reader also operates on them can then result in
incorrect memory access and various crashes.

Fix the problem by taking the reader_lock when updating a specific
ring_buffer_per_cpu in ring_buffer_subbuf_order_set().

Link: https://lore.kernel.org/linux-trace-kernel/20240715145141.5528-1-petr.pavlu@suse.com/
Link: https://lore.kernel.org/linux-trace-kernel/20241010195849.2f77cc3f@gandalf.local.home/
Link: https://lore.kernel.org/linux-trace-kernel/20241011112850.17212b25@gandalf.local.home/

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20241015112440.26987-1-petr.pavlu@suse.com
Fixes: 8e7b58c27b ("ring-buffer: Just update the subbuffers when changing their allocation order")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-10-15 11:18:51 -04:00

7605 lines
202 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Generic ring buffer
*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/trace_recursion.h>
#include <linux/trace_events.h>
#include <linux/ring_buffer.h>
#include <linux/trace_clock.h>
#include <linux/sched/clock.h>
#include <linux/cacheflush.h>
#include <linux/trace_seq.h>
#include <linux/spinlock.h>
#include <linux/irq_work.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/kthread.h> /* for self test */
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
#include <linux/cpu.h>
#include <linux/oom.h>
#include <linux/mm.h>
#include <asm/local64.h>
#include <asm/local.h>
#include "trace.h"
/*
* The "absolute" timestamp in the buffer is only 59 bits.
* If a clock has the 5 MSBs set, it needs to be saved and
* reinserted.
*/
#define TS_MSB (0xf8ULL << 56)
#define ABS_TS_MASK (~TS_MSB)
static void update_pages_handler(struct work_struct *work);
#define RING_BUFFER_META_MAGIC 0xBADFEED
struct ring_buffer_meta {
int magic;
int struct_size;
unsigned long text_addr;
unsigned long data_addr;
unsigned long first_buffer;
unsigned long head_buffer;
unsigned long commit_buffer;
__u32 subbuf_size;
__u32 nr_subbufs;
int buffers[];
};
/*
* The ring buffer header is special. We must manually up keep it.
*/
int ring_buffer_print_entry_header(struct trace_seq *s)
{
trace_seq_puts(s, "# compressed entry header\n");
trace_seq_puts(s, "\ttype_len : 5 bits\n");
trace_seq_puts(s, "\ttime_delta : 27 bits\n");
trace_seq_puts(s, "\tarray : 32 bits\n");
trace_seq_putc(s, '\n');
trace_seq_printf(s, "\tpadding : type == %d\n",
RINGBUF_TYPE_PADDING);
trace_seq_printf(s, "\ttime_extend : type == %d\n",
RINGBUF_TYPE_TIME_EXTEND);
trace_seq_printf(s, "\ttime_stamp : type == %d\n",
RINGBUF_TYPE_TIME_STAMP);
trace_seq_printf(s, "\tdata max type_len == %d\n",
RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
return !trace_seq_has_overflowed(s);
}
/*
* The ring buffer is made up of a list of pages. A separate list of pages is
* allocated for each CPU. A writer may only write to a buffer that is
* associated with the CPU it is currently executing on. A reader may read
* from any per cpu buffer.
*
* The reader is special. For each per cpu buffer, the reader has its own
* reader page. When a reader has read the entire reader page, this reader
* page is swapped with another page in the ring buffer.
*
* Now, as long as the writer is off the reader page, the reader can do what
* ever it wants with that page. The writer will never write to that page
* again (as long as it is out of the ring buffer).
*
* Here's some silly ASCII art.
*
* +------+
* |reader| RING BUFFER
* |page |
* +------+ +---+ +---+ +---+
* | |-->| |-->| |
* +---+ +---+ +---+
* ^ |
* | |
* +---------------+
*
*
* +------+
* |reader| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* | |-->| |-->| |
* +---+ +---+ +---+
* ^ |
* | |
* +---------------+
*
*
* +------+
* |reader| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* ^ | |-->| |-->| |
* | +---+ +---+ +---+
* | |
* | |
* +------------------------------+
*
*
* +------+
* |buffer| RING BUFFER
* |page |------------------v
* +------+ +---+ +---+ +---+
* ^ | | | |-->| |
* | New +---+ +---+ +---+
* | Reader------^ |
* | page |
* +------------------------------+
*
*
* After we make this swap, the reader can hand this page off to the splice
* code and be done with it. It can even allocate a new page if it needs to
* and swap that into the ring buffer.
*
* We will be using cmpxchg soon to make all this lockless.
*
*/
/* Used for individual buffers (after the counter) */
#define RB_BUFFER_OFF (1 << 20)
#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
# define RB_FORCE_8BYTE_ALIGNMENT 0
# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
#else
# define RB_FORCE_8BYTE_ALIGNMENT 1
# define RB_ARCH_ALIGNMENT 8U
#endif
#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
enum {
RB_LEN_TIME_EXTEND = 8,
RB_LEN_TIME_STAMP = 8,
};
#define skip_time_extend(event) \
((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
#define extended_time(event) \
(event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
static inline bool rb_null_event(struct ring_buffer_event *event)
{
return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
}
static void rb_event_set_padding(struct ring_buffer_event *event)
{
/* padding has a NULL time_delta */
event->type_len = RINGBUF_TYPE_PADDING;
event->time_delta = 0;
}
static unsigned
rb_event_data_length(struct ring_buffer_event *event)
{
unsigned length;
if (event->type_len)
length = event->type_len * RB_ALIGNMENT;
else
length = event->array[0];
return length + RB_EVNT_HDR_SIZE;
}
/*
* Return the length of the given event. Will return
* the length of the time extend if the event is a
* time extend.
*/
static inline unsigned
rb_event_length(struct ring_buffer_event *event)
{
switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
if (rb_null_event(event))
/* undefined */
return -1;
return event->array[0] + RB_EVNT_HDR_SIZE;
case RINGBUF_TYPE_TIME_EXTEND:
return RB_LEN_TIME_EXTEND;
case RINGBUF_TYPE_TIME_STAMP:
return RB_LEN_TIME_STAMP;
case RINGBUF_TYPE_DATA:
return rb_event_data_length(event);
default:
WARN_ON_ONCE(1);
}
/* not hit */
return 0;
}
/*
* Return total length of time extend and data,
* or just the event length for all other events.
*/
static inline unsigned
rb_event_ts_length(struct ring_buffer_event *event)
{
unsigned len = 0;
if (extended_time(event)) {
/* time extends include the data event after it */
len = RB_LEN_TIME_EXTEND;
event = skip_time_extend(event);
}
return len + rb_event_length(event);
}
/**
* ring_buffer_event_length - return the length of the event
* @event: the event to get the length of
*
* Returns the size of the data load of a data event.
* If the event is something other than a data event, it
* returns the size of the event itself. With the exception
* of a TIME EXTEND, where it still returns the size of the
* data load of the data event after it.
*/
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
unsigned length;
if (extended_time(event))
event = skip_time_extend(event);
length = rb_event_length(event);
if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
return length;
length -= RB_EVNT_HDR_SIZE;
if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
length -= sizeof(event->array[0]);
return length;
}
EXPORT_SYMBOL_GPL(ring_buffer_event_length);
/* inline for ring buffer fast paths */
static __always_inline void *
rb_event_data(struct ring_buffer_event *event)
{
if (extended_time(event))
event = skip_time_extend(event);
WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
/* If length is in len field, then array[0] has the data */
if (event->type_len)
return (void *)&event->array[0];
/* Otherwise length is in array[0] and array[1] has the data */
return (void *)&event->array[1];
}
/**
* ring_buffer_event_data - return the data of the event
* @event: the event to get the data from
*/
void *ring_buffer_event_data(struct ring_buffer_event *event)
{
return rb_event_data(event);
}
EXPORT_SYMBOL_GPL(ring_buffer_event_data);
#define for_each_buffer_cpu(buffer, cpu) \
for_each_cpu(cpu, buffer->cpumask)
#define for_each_online_buffer_cpu(buffer, cpu) \
for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
#define TS_SHIFT 27
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)
static u64 rb_event_time_stamp(struct ring_buffer_event *event)
{
u64 ts;
ts = event->array[0];
ts <<= TS_SHIFT;
ts += event->time_delta;
return ts;
}
/* Flag when events were overwritten */
#define RB_MISSED_EVENTS (1 << 31)
/* Missed count stored at end */
#define RB_MISSED_STORED (1 << 30)
#define RB_MISSED_MASK (3 << 30)
struct buffer_data_page {
u64 time_stamp; /* page time stamp */
local_t commit; /* write committed index */
unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
};
struct buffer_data_read_page {
unsigned order; /* order of the page */
struct buffer_data_page *data; /* actual data, stored in this page */
};
/*
* Note, the buffer_page list must be first. The buffer pages
* are allocated in cache lines, which means that each buffer
* page will be at the beginning of a cache line, and thus
* the least significant bits will be zero. We use this to
* add flags in the list struct pointers, to make the ring buffer
* lockless.
*/
struct buffer_page {
struct list_head list; /* list of buffer pages */
local_t write; /* index for next write */
unsigned read; /* index for next read */
local_t entries; /* entries on this page */
unsigned long real_end; /* real end of data */
unsigned order; /* order of the page */
u32 id:30; /* ID for external mapping */
u32 range:1; /* Mapped via a range */
struct buffer_data_page *page; /* Actual data page */
};
/*
* The buffer page counters, write and entries, must be reset
* atomically when crossing page boundaries. To synchronize this
* update, two counters are inserted into the number. One is
* the actual counter for the write position or count on the page.
*
* The other is a counter of updaters. Before an update happens
* the update partition of the counter is incremented. This will
* allow the updater to update the counter atomically.
*
* The counter is 20 bits, and the state data is 12.
*/
#define RB_WRITE_MASK 0xfffff
#define RB_WRITE_INTCNT (1 << 20)
static void rb_init_page(struct buffer_data_page *bpage)
{
local_set(&bpage->commit, 0);
}
static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
{
return local_read(&bpage->page->commit);
}
static void free_buffer_page(struct buffer_page *bpage)
{
/* Range pages are not to be freed */
if (!bpage->range)
free_pages((unsigned long)bpage->page, bpage->order);
kfree(bpage);
}
/*
* We need to fit the time_stamp delta into 27 bits.
*/
static inline bool test_time_stamp(u64 delta)
{
return !!(delta & TS_DELTA_TEST);
}
struct rb_irq_work {
struct irq_work work;
wait_queue_head_t waiters;
wait_queue_head_t full_waiters;
atomic_t seq;
bool waiters_pending;
bool full_waiters_pending;
bool wakeup_full;
};
/*
* Structure to hold event state and handle nested events.
*/
struct rb_event_info {
u64 ts;
u64 delta;
u64 before;
u64 after;
unsigned long length;
struct buffer_page *tail_page;
int add_timestamp;
};
/*
* Used for the add_timestamp
* NONE
* EXTEND - wants a time extend
* ABSOLUTE - the buffer requests all events to have absolute time stamps
* FORCE - force a full time stamp.
*/
enum {
RB_ADD_STAMP_NONE = 0,
RB_ADD_STAMP_EXTEND = BIT(1),
RB_ADD_STAMP_ABSOLUTE = BIT(2),
RB_ADD_STAMP_FORCE = BIT(3)
};
/*
* Used for which event context the event is in.
* TRANSITION = 0
* NMI = 1
* IRQ = 2
* SOFTIRQ = 3
* NORMAL = 4
*
* See trace_recursive_lock() comment below for more details.
*/
enum {
RB_CTX_TRANSITION,
RB_CTX_NMI,
RB_CTX_IRQ,
RB_CTX_SOFTIRQ,
RB_CTX_NORMAL,
RB_CTX_MAX
};
struct rb_time_struct {
local64_t time;
};
typedef struct rb_time_struct rb_time_t;
#define MAX_NEST 5
/*
* head_page == tail_page && head == tail then buffer is empty.
*/
struct ring_buffer_per_cpu {
int cpu;
atomic_t record_disabled;
atomic_t resize_disabled;
struct trace_buffer *buffer;
raw_spinlock_t reader_lock; /* serialize readers */
arch_spinlock_t lock;
struct lock_class_key lock_key;
struct buffer_data_page *free_page;
unsigned long nr_pages;
unsigned int current_context;
struct list_head *pages;
struct buffer_page *head_page; /* read from head */
struct buffer_page *tail_page; /* write to tail */
struct buffer_page *commit_page; /* committed pages */
struct buffer_page *reader_page;
unsigned long lost_events;
unsigned long last_overrun;
unsigned long nest;
local_t entries_bytes;
local_t entries;
local_t overrun;
local_t commit_overrun;
local_t dropped_events;
local_t committing;
local_t commits;
local_t pages_touched;
local_t pages_lost;
local_t pages_read;
long last_pages_touch;
size_t shortest_full;
unsigned long read;
unsigned long read_bytes;
rb_time_t write_stamp;
rb_time_t before_stamp;
u64 event_stamp[MAX_NEST];
u64 read_stamp;
/* pages removed since last reset */
unsigned long pages_removed;
unsigned int mapped;
unsigned int user_mapped; /* user space mapping */
struct mutex mapping_lock;
unsigned long *subbuf_ids; /* ID to subbuf VA */
struct trace_buffer_meta *meta_page;
struct ring_buffer_meta *ring_meta;
/* ring buffer pages to update, > 0 to add, < 0 to remove */
long nr_pages_to_update;
struct list_head new_pages; /* new pages to add */
struct work_struct update_pages_work;
struct completion update_done;
struct rb_irq_work irq_work;
};
struct trace_buffer {
unsigned flags;
int cpus;
atomic_t record_disabled;
atomic_t resizing;
cpumask_var_t cpumask;
struct lock_class_key *reader_lock_key;
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
struct hlist_node node;
u64 (*clock)(void);
struct rb_irq_work irq_work;
bool time_stamp_abs;
unsigned long range_addr_start;
unsigned long range_addr_end;
long last_text_delta;
long last_data_delta;
unsigned int subbuf_size;
unsigned int subbuf_order;
unsigned int max_data_size;
};
struct ring_buffer_iter {
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long head;
unsigned long next_event;
struct buffer_page *head_page;
struct buffer_page *cache_reader_page;
unsigned long cache_read;
unsigned long cache_pages_removed;
u64 read_stamp;
u64 page_stamp;
struct ring_buffer_event *event;
size_t event_size;
int missed_events;
};
int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
{
struct buffer_data_page field;
trace_seq_printf(s, "\tfield: u64 timestamp;\t"
"offset:0;\tsize:%u;\tsigned:%u;\n",
(unsigned int)sizeof(field.time_stamp),
(unsigned int)is_signed_type(u64));
trace_seq_printf(s, "\tfield: local_t commit;\t"
"offset:%u;\tsize:%u;\tsigned:%u;\n",
(unsigned int)offsetof(typeof(field), commit),
(unsigned int)sizeof(field.commit),
(unsigned int)is_signed_type(long));
trace_seq_printf(s, "\tfield: int overwrite;\t"
"offset:%u;\tsize:%u;\tsigned:%u;\n",
(unsigned int)offsetof(typeof(field), commit),
1,
(unsigned int)is_signed_type(long));
trace_seq_printf(s, "\tfield: char data;\t"
"offset:%u;\tsize:%u;\tsigned:%u;\n",
(unsigned int)offsetof(typeof(field), data),
(unsigned int)buffer->subbuf_size,
(unsigned int)is_signed_type(char));
return !trace_seq_has_overflowed(s);
}
static inline void rb_time_read(rb_time_t *t, u64 *ret)
{
*ret = local64_read(&t->time);
}
static void rb_time_set(rb_time_t *t, u64 val)
{
local64_set(&t->time, val);
}
/*
* Enable this to make sure that the event passed to
* ring_buffer_event_time_stamp() is not committed and also
* is on the buffer that it passed in.
*/
//#define RB_VERIFY_EVENT
#ifdef RB_VERIFY_EVENT
static struct list_head *rb_list_head(struct list_head *list);
static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
void *event)
{
struct buffer_page *page = cpu_buffer->commit_page;
struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
struct list_head *next;
long commit, write;
unsigned long addr = (unsigned long)event;
bool done = false;
int stop = 0;
/* Make sure the event exists and is not committed yet */
do {
if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
done = true;
commit = local_read(&page->page->commit);
write = local_read(&page->write);
if (addr >= (unsigned long)&page->page->data[commit] &&
addr < (unsigned long)&page->page->data[write])
return;
next = rb_list_head(page->list.next);
page = list_entry(next, struct buffer_page, list);
} while (!done);
WARN_ON_ONCE(1);
}
#else
static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
void *event)
{
}
#endif
/*
* The absolute time stamp drops the 5 MSBs and some clocks may
* require them. The rb_fix_abs_ts() will take a previous full
* time stamp, and add the 5 MSB of that time stamp on to the
* saved absolute time stamp. Then they are compared in case of
* the unlikely event that the latest time stamp incremented
* the 5 MSB.
*/
static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
{
if (save_ts & TS_MSB) {
abs |= save_ts & TS_MSB;
/* Check for overflow */
if (unlikely(abs < save_ts))
abs += 1ULL << 59;
}
return abs;
}
static inline u64 rb_time_stamp(struct trace_buffer *buffer);
/**
* ring_buffer_event_time_stamp - return the event's current time stamp
* @buffer: The buffer that the event is on
* @event: the event to get the time stamp of
*
* Note, this must be called after @event is reserved, and before it is
* committed to the ring buffer. And must be called from the same
* context where the event was reserved (normal, softirq, irq, etc).
*
* Returns the time stamp associated with the current event.
* If the event has an extended time stamp, then that is used as
* the time stamp to return.
* In the highly unlikely case that the event was nested more than
* the max nesting, then the write_stamp of the buffer is returned,
* otherwise current time is returned, but that really neither of
* the last two cases should ever happen.
*/
u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
struct ring_buffer_event *event)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
unsigned int nest;
u64 ts;
/* If the event includes an absolute time, then just use that */
if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
ts = rb_event_time_stamp(event);
return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
}
nest = local_read(&cpu_buffer->committing);
verify_event(cpu_buffer, event);
if (WARN_ON_ONCE(!nest))
goto fail;
/* Read the current saved nesting level time stamp */
if (likely(--nest < MAX_NEST))
return cpu_buffer->event_stamp[nest];
/* Shouldn't happen, warn if it does */
WARN_ONCE(1, "nest (%d) greater than max", nest);
fail:
rb_time_read(&cpu_buffer->write_stamp, &ts);
return ts;
}
/**
* ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
* @buffer: The ring_buffer to get the number of pages from
* @cpu: The cpu of the ring_buffer to get the number of pages from
*
* Returns the number of pages that have content in the ring buffer.
*/
size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
{
size_t read;
size_t lost;
size_t cnt;
read = local_read(&buffer->buffers[cpu]->pages_read);
lost = local_read(&buffer->buffers[cpu]->pages_lost);
cnt = local_read(&buffer->buffers[cpu]->pages_touched);
if (WARN_ON_ONCE(cnt < lost))
return 0;
cnt -= lost;
/* The reader can read an empty page, but not more than that */
if (cnt < read) {
WARN_ON_ONCE(read > cnt + 1);
return 0;
}
return cnt - read;
}
static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
size_t nr_pages;
size_t dirty;
nr_pages = cpu_buffer->nr_pages;
if (!nr_pages || !full)
return true;
/*
* Add one as dirty will never equal nr_pages, as the sub-buffer
* that the writer is on is not counted as dirty.
* This is needed if "buffer_percent" is set to 100.
*/
dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
return (dirty * 100) >= (full * nr_pages);
}
/*
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
*
* Schedules a delayed work to wake up any task that is blocked on the
* ring buffer waiters queue.
*/
static void rb_wake_up_waiters(struct irq_work *work)
{
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
/* For waiters waiting for the first wake up */
(void)atomic_fetch_inc_release(&rbwork->seq);
wake_up_all(&rbwork->waiters);
if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
/* Only cpu_buffer sets the above flags */
struct ring_buffer_per_cpu *cpu_buffer =
container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
/* Called from interrupt context */
raw_spin_lock(&cpu_buffer->reader_lock);
rbwork->wakeup_full = false;
rbwork->full_waiters_pending = false;
/* Waking up all waiters, they will reset the shortest full */
cpu_buffer->shortest_full = 0;
raw_spin_unlock(&cpu_buffer->reader_lock);
wake_up_all(&rbwork->full_waiters);
}
}
/**
* ring_buffer_wake_waiters - wake up any waiters on this ring buffer
* @buffer: The ring buffer to wake waiters on
* @cpu: The CPU buffer to wake waiters on
*
* In the case of a file that represents a ring buffer is closing,
* it is prudent to wake up any waiters that are on this.
*/
void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct rb_irq_work *rbwork;
if (!buffer)
return;
if (cpu == RING_BUFFER_ALL_CPUS) {
/* Wake up individual ones too. One level recursion */
for_each_buffer_cpu(buffer, cpu)
ring_buffer_wake_waiters(buffer, cpu);
rbwork = &buffer->irq_work;
} else {
if (WARN_ON_ONCE(!buffer->buffers))
return;
if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
return;
cpu_buffer = buffer->buffers[cpu];
/* The CPU buffer may not have been initialized yet */
if (!cpu_buffer)
return;
rbwork = &cpu_buffer->irq_work;
}
/* This can be called in any context */
irq_work_queue(&rbwork->work);
}
static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
{
struct ring_buffer_per_cpu *cpu_buffer;
bool ret = false;
/* Reads of all CPUs always waits for any data */
if (cpu == RING_BUFFER_ALL_CPUS)
return !ring_buffer_empty(buffer);
cpu_buffer = buffer->buffers[cpu];
if (!ring_buffer_empty_cpu(buffer, cpu)) {
unsigned long flags;
bool pagebusy;
if (!full)
return true;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
ret = !pagebusy && full_hit(buffer, cpu, full);
if (!ret && (!cpu_buffer->shortest_full ||
cpu_buffer->shortest_full > full)) {
cpu_buffer->shortest_full = full;
}
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
return ret;
}
static inline bool
rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
int cpu, int full, ring_buffer_cond_fn cond, void *data)
{
if (rb_watermark_hit(buffer, cpu, full))
return true;
if (cond(data))
return true;
/*
* The events can happen in critical sections where
* checking a work queue can cause deadlocks.
* After adding a task to the queue, this flag is set
* only to notify events to try to wake up the queue
* using irq_work.
*
* We don't clear it even if the buffer is no longer
* empty. The flag only causes the next event to run
* irq_work to do the work queue wake up. The worse
* that can happen if we race with !trace_empty() is that
* an event will cause an irq_work to try to wake up
* an empty queue.
*
* There's no reason to protect this flag either, as
* the work queue and irq_work logic will do the necessary
* synchronization for the wake ups. The only thing
* that is necessary is that the wake up happens after
* a task has been queued. It's OK for spurious wake ups.
*/
if (full)
rbwork->full_waiters_pending = true;
else
rbwork->waiters_pending = true;
return false;
}
struct rb_wait_data {
struct rb_irq_work *irq_work;
int seq;
};
/*
* The default wait condition for ring_buffer_wait() is to just to exit the
* wait loop the first time it is woken up.
*/
static bool rb_wait_once(void *data)
{
struct rb_wait_data *rdata = data;
struct rb_irq_work *rbwork = rdata->irq_work;
return atomic_read_acquire(&rbwork->seq) != rdata->seq;
}
/**
* ring_buffer_wait - wait for input to the ring buffer
* @buffer: buffer to wait on
* @cpu: the cpu buffer to wait on
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
* @cond: condition function to break out of wait (NULL to run once)
* @data: the data to pass to @cond.
*
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
* as data is added to any of the @buffer's cpu buffers. Otherwise
* it will wait for data to be added to a specific cpu buffer.
*/
int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
ring_buffer_cond_fn cond, void *data)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct wait_queue_head *waitq;
struct rb_irq_work *rbwork;
struct rb_wait_data rdata;
int ret = 0;
/*
* Depending on what the caller is waiting for, either any
* data in any cpu buffer, or a specific buffer, put the
* caller on the appropriate wait queue.
*/
if (cpu == RING_BUFFER_ALL_CPUS) {
rbwork = &buffer->irq_work;
/* Full only makes sense on per cpu reads */
full = 0;
} else {
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return -ENODEV;
cpu_buffer = buffer->buffers[cpu];
rbwork = &cpu_buffer->irq_work;
}
if (full)
waitq = &rbwork->full_waiters;
else
waitq = &rbwork->waiters;
/* Set up to exit loop as soon as it is woken */
if (!cond) {
cond = rb_wait_once;
rdata.irq_work = rbwork;
rdata.seq = atomic_read_acquire(&rbwork->seq);
data = &rdata;
}
ret = wait_event_interruptible((*waitq),
rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
return ret;
}
/**
* ring_buffer_poll_wait - poll on buffer input
* @buffer: buffer to wait on
* @cpu: the cpu buffer to wait on
* @filp: the file descriptor
* @poll_table: The poll descriptor
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
*
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
* as data is added to any of the @buffer's cpu buffers. Otherwise
* it will wait for data to be added to a specific cpu buffer.
*
* Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
* zero otherwise.
*/
__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
struct file *filp, poll_table *poll_table, int full)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct rb_irq_work *rbwork;
if (cpu == RING_BUFFER_ALL_CPUS) {
rbwork = &buffer->irq_work;
full = 0;
} else {
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return EPOLLERR;
cpu_buffer = buffer->buffers[cpu];
rbwork = &cpu_buffer->irq_work;
}
if (full) {
poll_wait(filp, &rbwork->full_waiters, poll_table);
if (rb_watermark_hit(buffer, cpu, full))
return EPOLLIN | EPOLLRDNORM;
/*
* Only allow full_waiters_pending update to be seen after
* the shortest_full is set (in rb_watermark_hit). If the
* writer sees the full_waiters_pending flag set, it will
* compare the amount in the ring buffer to shortest_full.
* If the amount in the ring buffer is greater than the
* shortest_full percent, it will call the irq_work handler
* to wake up this list. The irq_handler will reset shortest_full
* back to zero. That's done under the reader_lock, but
* the below smp_mb() makes sure that the update to
* full_waiters_pending doesn't leak up into the above.
*/
smp_mb();
rbwork->full_waiters_pending = true;
return 0;
}
poll_wait(filp, &rbwork->waiters, poll_table);
rbwork->waiters_pending = true;
/*
* There's a tight race between setting the waiters_pending and
* checking if the ring buffer is empty. Once the waiters_pending bit
* is set, the next event will wake the task up, but we can get stuck
* if there's only a single event in.
*
* FIXME: Ideally, we need a memory barrier on the writer side as well,
* but adding a memory barrier to all events will cause too much of a
* performance hit in the fast path. We only need a memory barrier when
* the buffer goes from empty to having content. But as this race is
* extremely small, and it's not a problem if another event comes in, we
* will fix it later.
*/
smp_mb();
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
return EPOLLIN | EPOLLRDNORM;
return 0;
}
/* buffer may be either ring_buffer or ring_buffer_per_cpu */
#define RB_WARN_ON(b, cond) \
({ \
int _____ret = unlikely(cond); \
if (_____ret) { \
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
struct ring_buffer_per_cpu *__b = \
(void *)b; \
atomic_inc(&__b->buffer->record_disabled); \
} else \
atomic_inc(&b->record_disabled); \
WARN_ON(1); \
} \
_____ret; \
})
/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0
static inline u64 rb_time_stamp(struct trace_buffer *buffer)
{
u64 ts;
/* Skip retpolines :-( */
if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
ts = trace_clock_local();
else
ts = buffer->clock();
/* shift to debug/test normalization and TIME_EXTENTS */
return ts << DEBUG_SHIFT;
}
u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
{
u64 time;
preempt_disable_notrace();
time = rb_time_stamp(buffer);
preempt_enable_notrace();
return time;
}
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
int cpu, u64 *ts)
{
/* Just stupid testing the normalize function and deltas */
*ts >>= DEBUG_SHIFT;
}
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
/*
* Making the ring buffer lockless makes things tricky.
* Although writes only happen on the CPU that they are on,
* and they only need to worry about interrupts. Reads can
* happen on any CPU.
*
* The reader page is always off the ring buffer, but when the
* reader finishes with a page, it needs to swap its page with
* a new one from the buffer. The reader needs to take from
* the head (writes go to the tail). But if a writer is in overwrite
* mode and wraps, it must push the head page forward.
*
* Here lies the problem.
*
* The reader must be careful to replace only the head page, and
* not another one. As described at the top of the file in the
* ASCII art, the reader sets its old page to point to the next
* page after head. It then sets the page after head to point to
* the old reader page. But if the writer moves the head page
* during this operation, the reader could end up with the tail.
*
* We use cmpxchg to help prevent this race. We also do something
* special with the page before head. We set the LSB to 1.
*
* When the writer must push the page forward, it will clear the
* bit that points to the head page, move the head, and then set
* the bit that points to the new head page.
*
* We also don't want an interrupt coming in and moving the head
* page on another writer. Thus we use the second LSB to catch
* that too. Thus:
*
* head->list->prev->next bit 1 bit 0
* ------- -------
* Normal page 0 0
* Points to head page 0 1
* New head page 1 0
*
* Note we can not trust the prev pointer of the head page, because:
*
* +----+ +-----+ +-----+
* | |------>| T |---X--->| N |
* | |<------| | | |
* +----+ +-----+ +-----+
* ^ ^ |
* | +-----+ | |
* +----------| R |----------+ |
* | |<-----------+
* +-----+
*
* Key: ---X--> HEAD flag set in pointer
* T Tail page
* R Reader page
* N Next page
*
* (see __rb_reserve_next() to see where this happens)
*
* What the above shows is that the reader just swapped out
* the reader page with a page in the buffer, but before it
* could make the new header point back to the new page added
* it was preempted by a writer. The writer moved forward onto
* the new page added by the reader and is about to move forward
* again.
*
* You can see, it is legitimate for the previous pointer of
* the head (or any page) not to point back to itself. But only
* temporarily.
*/
#define RB_PAGE_NORMAL 0UL
#define RB_PAGE_HEAD 1UL
#define RB_PAGE_UPDATE 2UL
#define RB_FLAG_MASK 3UL
/* PAGE_MOVED is not part of the mask */
#define RB_PAGE_MOVED 4UL
/*
* rb_list_head - remove any bit
*/
static struct list_head *rb_list_head(struct list_head *list)
{
unsigned long val = (unsigned long)list;
return (struct list_head *)(val & ~RB_FLAG_MASK);
}
/*
* rb_is_head_page - test if the given page is the head page
*
* Because the reader may move the head_page pointer, we can
* not trust what the head page is (it may be pointing to
* the reader page). But if the next page is a header page,
* its flags will be non zero.
*/
static inline int
rb_is_head_page(struct buffer_page *page, struct list_head *list)
{
unsigned long val;
val = (unsigned long)list->next;
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
return RB_PAGE_MOVED;
return val & RB_FLAG_MASK;
}
/*
* rb_is_reader_page
*
* The unique thing about the reader page, is that, if the
* writer is ever on it, the previous pointer never points
* back to the reader page.
*/
static bool rb_is_reader_page(struct buffer_page *page)
{
struct list_head *list = page->list.prev;
return rb_list_head(list->next) != &page->list;
}
/*
* rb_set_list_to_head - set a list_head to be pointing to head.
*/
static void rb_set_list_to_head(struct list_head *list)
{
unsigned long *ptr;
ptr = (unsigned long *)&list->next;
*ptr |= RB_PAGE_HEAD;
*ptr &= ~RB_PAGE_UPDATE;
}
/*
* rb_head_page_activate - sets up head page
*/
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *head;
head = cpu_buffer->head_page;
if (!head)
return;
/*
* Set the previous list pointer to have the HEAD flag.
*/
rb_set_list_to_head(head->list.prev);
if (cpu_buffer->ring_meta) {
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
meta->head_buffer = (unsigned long)head->page;
}
}
static void rb_list_head_clear(struct list_head *list)
{
unsigned long *ptr = (unsigned long *)&list->next;
*ptr &= ~RB_FLAG_MASK;
}
/*
* rb_head_page_deactivate - clears head page ptr (for free list)
*/
static void
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
{
struct list_head *hd;
/* Go through the whole list and clear any pointers found. */
rb_list_head_clear(cpu_buffer->pages);
list_for_each(hd, cpu_buffer->pages)
rb_list_head_clear(hd);
}
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag, int new_flag)
{
struct list_head *list;
unsigned long val = (unsigned long)&head->list;
unsigned long ret;
list = &prev->list;
val &= ~RB_FLAG_MASK;
ret = cmpxchg((unsigned long *)&list->next,
val | old_flag, val | new_flag);
/* check if the reader took the page */
if ((ret & ~RB_FLAG_MASK) != val)
return RB_PAGE_MOVED;
return ret & RB_FLAG_MASK;
}
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_UPDATE);
}
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_HEAD);
}
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *head,
struct buffer_page *prev,
int old_flag)
{
return rb_head_page_set(cpu_buffer, head, prev,
old_flag, RB_PAGE_NORMAL);
}
static inline void rb_inc_page(struct buffer_page **bpage)
{
struct list_head *p = rb_list_head((*bpage)->list.next);
*bpage = list_entry(p, struct buffer_page, list);
}
static struct buffer_page *
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *head;
struct buffer_page *page;
struct list_head *list;
int i;
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
return NULL;
/* sanity check */
list = cpu_buffer->pages;
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
return NULL;
page = head = cpu_buffer->head_page;
/*
* It is possible that the writer moves the header behind
* where we started, and we miss in one loop.
* A second loop should grab the header, but we'll do
* three loops just because I'm paranoid.
*/
for (i = 0; i < 3; i++) {
do {
if (rb_is_head_page(page, page->list.prev)) {
cpu_buffer->head_page = page;
return page;
}
rb_inc_page(&page);
} while (page != head);
}
RB_WARN_ON(cpu_buffer, 1);
return NULL;
}
static bool rb_head_page_replace(struct buffer_page *old,
struct buffer_page *new)
{
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
unsigned long val;
val = *ptr & ~RB_FLAG_MASK;
val |= RB_PAGE_HEAD;
return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
}
/*
* rb_tail_page_update - move the tail page forward
*/
static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *tail_page,
struct buffer_page *next_page)
{
unsigned long old_entries;
unsigned long old_write;
/*
* The tail page now needs to be moved forward.
*
* We need to reset the tail page, but without messing
* with possible erasing of data brought in by interrupts
* that have moved the tail page and are currently on it.
*
* We add a counter to the write field to denote this.
*/
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
/*
* Just make sure we have seen our old_write and synchronize
* with any interrupts that come in.
*/
barrier();
/*
* If the tail page is still the same as what we think
* it is, then it is up to us to update the tail
* pointer.
*/
if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
/* Zero the write counter */
unsigned long val = old_write & ~RB_WRITE_MASK;
unsigned long eval = old_entries & ~RB_WRITE_MASK;
/*
* This will only succeed if an interrupt did
* not come in and change it. In which case, we
* do not want to modify it.
*
* We add (void) to let the compiler know that we do not care
* about the return value of these functions. We use the
* cmpxchg to only update if an interrupt did not already
* do it for us. If the cmpxchg fails, we don't care.
*/
(void)local_cmpxchg(&next_page->write, old_write, val);
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
/*
* No need to worry about races with clearing out the commit.
* it only can increment when a commit takes place. But that
* only happens in the outer most nested commit.
*/
local_set(&next_page->page->commit, 0);
/* Either we update tail_page or an interrupt does */
if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
local_inc(&cpu_buffer->pages_touched);
}
}
static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *bpage)
{
unsigned long val = (unsigned long)bpage;
RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
}
/**
* rb_check_pages - integrity check of buffer pages
* @cpu_buffer: CPU buffer with pages to test
*
* As a safety measure we check to make sure the data pages have not
* been corrupted.
*
* Callers of this function need to guarantee that the list of pages doesn't get
* modified during the check. In particular, if it's possible that the function
* is invoked with concurrent readers which can swap in a new reader page then
* the caller should take cpu_buffer->reader_lock.
*/
static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
struct list_head *head = rb_list_head(cpu_buffer->pages);
struct list_head *tmp;
if (RB_WARN_ON(cpu_buffer,
rb_list_head(rb_list_head(head->next)->prev) != head))
return;
if (RB_WARN_ON(cpu_buffer,
rb_list_head(rb_list_head(head->prev)->next) != head))
return;
for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) {
if (RB_WARN_ON(cpu_buffer,
rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
return;
if (RB_WARN_ON(cpu_buffer,
rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
return;
}
}
/*
* Take an address, add the meta data size as well as the array of
* array subbuffer indexes, then align it to a subbuffer size.
*
* This is used to help find the next per cpu subbuffer within a mapped range.
*/
static unsigned long
rb_range_align_subbuf(unsigned long addr, int subbuf_size, int nr_subbufs)
{
addr += sizeof(struct ring_buffer_meta) +
sizeof(int) * nr_subbufs;
return ALIGN(addr, subbuf_size);
}
/*
* Return the ring_buffer_meta for a given @cpu.
*/
static void *rb_range_meta(struct trace_buffer *buffer, int nr_pages, int cpu)
{
int subbuf_size = buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
unsigned long ptr = buffer->range_addr_start;
struct ring_buffer_meta *meta;
int nr_subbufs;
if (!ptr)
return NULL;
/* When nr_pages passed in is zero, the first meta has already been initialized */
if (!nr_pages) {
meta = (struct ring_buffer_meta *)ptr;
nr_subbufs = meta->nr_subbufs;
} else {
meta = NULL;
/* Include the reader page */
nr_subbufs = nr_pages + 1;
}
/*
* The first chunk may not be subbuffer aligned, where as
* the rest of the chunks are.
*/
if (cpu) {
ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
ptr += subbuf_size * nr_subbufs;
/* We can use multiplication to find chunks greater than 1 */
if (cpu > 1) {
unsigned long size;
unsigned long p;
/* Save the beginning of this CPU chunk */
p = ptr;
ptr = rb_range_align_subbuf(ptr, subbuf_size, nr_subbufs);
ptr += subbuf_size * nr_subbufs;
/* Now all chunks after this are the same size */
size = ptr - p;
ptr += size * (cpu - 2);
}
}
return (void *)ptr;
}
/* Return the start of subbufs given the meta pointer */
static void *rb_subbufs_from_meta(struct ring_buffer_meta *meta)
{
int subbuf_size = meta->subbuf_size;
unsigned long ptr;
ptr = (unsigned long)meta;
ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs);
return (void *)ptr;
}
/*
* Return a specific sub-buffer for a given @cpu defined by @idx.
*/
static void *rb_range_buffer(struct ring_buffer_per_cpu *cpu_buffer, int idx)
{
struct ring_buffer_meta *meta;
unsigned long ptr;
int subbuf_size;
meta = rb_range_meta(cpu_buffer->buffer, 0, cpu_buffer->cpu);
if (!meta)
return NULL;
if (WARN_ON_ONCE(idx >= meta->nr_subbufs))
return NULL;
subbuf_size = meta->subbuf_size;
/* Map this buffer to the order that's in meta->buffers[] */
idx = meta->buffers[idx];
ptr = (unsigned long)rb_subbufs_from_meta(meta);
ptr += subbuf_size * idx;
if (ptr + subbuf_size > cpu_buffer->buffer->range_addr_end)
return NULL;
return (void *)ptr;
}
/*
* See if the existing memory contains valid ring buffer data.
* As the previous kernel must be the same as this kernel, all
* the calculations (size of buffers and number of buffers)
* must be the same.
*/
static bool rb_meta_valid(struct ring_buffer_meta *meta, int cpu,
struct trace_buffer *buffer, int nr_pages)
{
int subbuf_size = PAGE_SIZE;
struct buffer_data_page *subbuf;
unsigned long buffers_start;
unsigned long buffers_end;
int i;
/* Check the meta magic and meta struct size */
if (meta->magic != RING_BUFFER_META_MAGIC ||
meta->struct_size != sizeof(*meta)) {
pr_info("Ring buffer boot meta[%d] mismatch of magic or struct size\n", cpu);
return false;
}
/* The subbuffer's size and number of subbuffers must match */
if (meta->subbuf_size != subbuf_size ||
meta->nr_subbufs != nr_pages + 1) {
pr_info("Ring buffer boot meta [%d] mismatch of subbuf_size/nr_pages\n", cpu);
return false;
}
buffers_start = meta->first_buffer;
buffers_end = meta->first_buffer + (subbuf_size * meta->nr_subbufs);
/* Is the head and commit buffers within the range of buffers? */
if (meta->head_buffer < buffers_start ||
meta->head_buffer >= buffers_end) {
pr_info("Ring buffer boot meta [%d] head buffer out of range\n", cpu);
return false;
}
if (meta->commit_buffer < buffers_start ||
meta->commit_buffer >= buffers_end) {
pr_info("Ring buffer boot meta [%d] commit buffer out of range\n", cpu);
return false;
}
subbuf = rb_subbufs_from_meta(meta);
/* Is the meta buffers and the subbufs themselves have correct data? */
for (i = 0; i < meta->nr_subbufs; i++) {
if (meta->buffers[i] < 0 ||
meta->buffers[i] >= meta->nr_subbufs) {
pr_info("Ring buffer boot meta [%d] array out of range\n", cpu);
return false;
}
if ((unsigned)local_read(&subbuf->commit) > subbuf_size) {
pr_info("Ring buffer boot meta [%d] buffer invalid commit\n", cpu);
return false;
}
subbuf = (void *)subbuf + subbuf_size;
}
return true;
}
static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf);
static int rb_read_data_buffer(struct buffer_data_page *dpage, int tail, int cpu,
unsigned long long *timestamp, u64 *delta_ptr)
{
struct ring_buffer_event *event;
u64 ts, delta;
int events = 0;
int e;
*delta_ptr = 0;
*timestamp = 0;
ts = dpage->time_stamp;
for (e = 0; e < tail; e += rb_event_length(event)) {
event = (struct ring_buffer_event *)(dpage->data + e);
switch (event->type_len) {
case RINGBUF_TYPE_TIME_EXTEND:
delta = rb_event_time_stamp(event);
ts += delta;
break;
case RINGBUF_TYPE_TIME_STAMP:
delta = rb_event_time_stamp(event);
delta = rb_fix_abs_ts(delta, ts);
if (delta < ts) {
*delta_ptr = delta;
*timestamp = ts;
return -1;
}
ts = delta;
break;
case RINGBUF_TYPE_PADDING:
if (event->time_delta == 1)
break;
fallthrough;
case RINGBUF_TYPE_DATA:
events++;
ts += event->time_delta;
break;
default:
return -1;
}
}
*timestamp = ts;
return events;
}
static int rb_validate_buffer(struct buffer_data_page *dpage, int cpu)
{
unsigned long long ts;
u64 delta;
int tail;
tail = local_read(&dpage->commit);
return rb_read_data_buffer(dpage, tail, cpu, &ts, &delta);
}
/* If the meta data has been validated, now validate the events */
static void rb_meta_validate_events(struct ring_buffer_per_cpu *cpu_buffer)
{
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
struct buffer_page *head_page;
unsigned long entry_bytes = 0;
unsigned long entries = 0;
int ret;
int i;
if (!meta || !meta->head_buffer)
return;
/* Do the reader page first */
ret = rb_validate_buffer(cpu_buffer->reader_page->page, cpu_buffer->cpu);
if (ret < 0) {
pr_info("Ring buffer reader page is invalid\n");
goto invalid;
}
entries += ret;
entry_bytes += local_read(&cpu_buffer->reader_page->page->commit);
local_set(&cpu_buffer->reader_page->entries, ret);
head_page = cpu_buffer->head_page;
/* If both the head and commit are on the reader_page then we are done. */
if (head_page == cpu_buffer->reader_page &&
head_page == cpu_buffer->commit_page)
goto done;
/* Iterate until finding the commit page */
for (i = 0; i < meta->nr_subbufs + 1; i++, rb_inc_page(&head_page)) {
/* Reader page has already been done */
if (head_page == cpu_buffer->reader_page)
continue;
ret = rb_validate_buffer(head_page->page, cpu_buffer->cpu);
if (ret < 0) {
pr_info("Ring buffer meta [%d] invalid buffer page\n",
cpu_buffer->cpu);
goto invalid;
}
entries += ret;
entry_bytes += local_read(&head_page->page->commit);
local_set(&cpu_buffer->head_page->entries, ret);
if (head_page == cpu_buffer->commit_page)
break;
}
if (head_page != cpu_buffer->commit_page) {
pr_info("Ring buffer meta [%d] commit page not found\n",
cpu_buffer->cpu);
goto invalid;
}
done:
local_set(&cpu_buffer->entries, entries);
local_set(&cpu_buffer->entries_bytes, entry_bytes);
pr_info("Ring buffer meta [%d] is from previous boot!\n", cpu_buffer->cpu);
return;
invalid:
/* The content of the buffers are invalid, reset the meta data */
meta->head_buffer = 0;
meta->commit_buffer = 0;
/* Reset the reader page */
local_set(&cpu_buffer->reader_page->entries, 0);
local_set(&cpu_buffer->reader_page->page->commit, 0);
/* Reset all the subbuffers */
for (i = 0; i < meta->nr_subbufs - 1; i++, rb_inc_page(&head_page)) {
local_set(&head_page->entries, 0);
local_set(&head_page->page->commit, 0);
}
}
/* Used to calculate data delta */
static char rb_data_ptr[] = "";
#define THIS_TEXT_PTR ((unsigned long)rb_meta_init_text_addr)
#define THIS_DATA_PTR ((unsigned long)rb_data_ptr)
static void rb_meta_init_text_addr(struct ring_buffer_meta *meta)
{
meta->text_addr = THIS_TEXT_PTR;
meta->data_addr = THIS_DATA_PTR;
}
static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages)
{
struct ring_buffer_meta *meta;
unsigned long delta;
void *subbuf;
int cpu;
int i;
for (cpu = 0; cpu < nr_cpu_ids; cpu++) {
void *next_meta;
meta = rb_range_meta(buffer, nr_pages, cpu);
if (rb_meta_valid(meta, cpu, buffer, nr_pages)) {
/* Make the mappings match the current address */
subbuf = rb_subbufs_from_meta(meta);
delta = (unsigned long)subbuf - meta->first_buffer;
meta->first_buffer += delta;
meta->head_buffer += delta;
meta->commit_buffer += delta;
buffer->last_text_delta = THIS_TEXT_PTR - meta->text_addr;
buffer->last_data_delta = THIS_DATA_PTR - meta->data_addr;
continue;
}
if (cpu < nr_cpu_ids - 1)
next_meta = rb_range_meta(buffer, nr_pages, cpu + 1);
else
next_meta = (void *)buffer->range_addr_end;
memset(meta, 0, next_meta - (void *)meta);
meta->magic = RING_BUFFER_META_MAGIC;
meta->struct_size = sizeof(*meta);
meta->nr_subbufs = nr_pages + 1;
meta->subbuf_size = PAGE_SIZE;
subbuf = rb_subbufs_from_meta(meta);
meta->first_buffer = (unsigned long)subbuf;
rb_meta_init_text_addr(meta);
/*
* The buffers[] array holds the order of the sub-buffers
* that are after the meta data. The sub-buffers may
* be swapped out when read and inserted into a different
* location of the ring buffer. Although their addresses
* remain the same, the buffers[] array contains the
* index into the sub-buffers holding their actual order.
*/
for (i = 0; i < meta->nr_subbufs; i++) {
meta->buffers[i] = i;
rb_init_page(subbuf);
subbuf += meta->subbuf_size;
}
}
}
static void *rbm_start(struct seq_file *m, loff_t *pos)
{
struct ring_buffer_per_cpu *cpu_buffer = m->private;
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
unsigned long val;
if (!meta)
return NULL;
if (*pos > meta->nr_subbufs)
return NULL;
val = *pos;
val++;
return (void *)val;
}
static void *rbm_next(struct seq_file *m, void *v, loff_t *pos)
{
(*pos)++;
return rbm_start(m, pos);
}
static int rbm_show(struct seq_file *m, void *v)
{
struct ring_buffer_per_cpu *cpu_buffer = m->private;
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
unsigned long val = (unsigned long)v;
if (val == 1) {
seq_printf(m, "head_buffer: %d\n",
rb_meta_subbuf_idx(meta, (void *)meta->head_buffer));
seq_printf(m, "commit_buffer: %d\n",
rb_meta_subbuf_idx(meta, (void *)meta->commit_buffer));
seq_printf(m, "subbuf_size: %d\n", meta->subbuf_size);
seq_printf(m, "nr_subbufs: %d\n", meta->nr_subbufs);
return 0;
}
val -= 2;
seq_printf(m, "buffer[%ld]: %d\n", val, meta->buffers[val]);
return 0;
}
static void rbm_stop(struct seq_file *m, void *p)
{
}
static const struct seq_operations rb_meta_seq_ops = {
.start = rbm_start,
.next = rbm_next,
.show = rbm_show,
.stop = rbm_stop,
};
int ring_buffer_meta_seq_init(struct file *file, struct trace_buffer *buffer, int cpu)
{
struct seq_file *m;
int ret;
ret = seq_open(file, &rb_meta_seq_ops);
if (ret)
return ret;
m = file->private_data;
m->private = buffer->buffers[cpu];
return 0;
}
/* Map the buffer_pages to the previous head and commit pages */
static void rb_meta_buffer_update(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *bpage)
{
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
if (meta->head_buffer == (unsigned long)bpage->page)
cpu_buffer->head_page = bpage;
if (meta->commit_buffer == (unsigned long)bpage->page) {
cpu_buffer->commit_page = bpage;
cpu_buffer->tail_page = bpage;
}
}
static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
long nr_pages, struct list_head *pages)
{
struct trace_buffer *buffer = cpu_buffer->buffer;
struct ring_buffer_meta *meta = NULL;
struct buffer_page *bpage, *tmp;
bool user_thread = current->mm != NULL;
gfp_t mflags;
long i;
/*
* Check if the available memory is there first.
* Note, si_mem_available() only gives us a rough estimate of available
* memory. It may not be accurate. But we don't care, we just want
* to prevent doing any allocation when it is obvious that it is
* not going to succeed.
*/
i = si_mem_available();
if (i < nr_pages)
return -ENOMEM;
/*
* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
* gracefully without invoking oom-killer and the system is not
* destabilized.
*/
mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
/*
* If a user thread allocates too much, and si_mem_available()
* reports there's enough memory, even though there is not.
* Make sure the OOM killer kills this thread. This can happen
* even with RETRY_MAYFAIL because another task may be doing
* an allocation after this task has taken all memory.
* This is the task the OOM killer needs to take out during this
* loop, even if it was triggered by an allocation somewhere else.
*/
if (user_thread)
set_current_oom_origin();
if (buffer->range_addr_start)
meta = rb_range_meta(buffer, nr_pages, cpu_buffer->cpu);
for (i = 0; i < nr_pages; i++) {
struct page *page;
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
mflags, cpu_to_node(cpu_buffer->cpu));
if (!bpage)
goto free_pages;
rb_check_bpage(cpu_buffer, bpage);
/*
* Append the pages as for mapped buffers we want to keep
* the order
*/
list_add_tail(&bpage->list, pages);
if (meta) {
/* A range was given. Use that for the buffer page */
bpage->page = rb_range_buffer(cpu_buffer, i + 1);
if (!bpage->page)
goto free_pages;
/* If this is valid from a previous boot */
if (meta->head_buffer)
rb_meta_buffer_update(cpu_buffer, bpage);
bpage->range = 1;
bpage->id = i + 1;
} else {
page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
mflags | __GFP_COMP | __GFP_ZERO,
cpu_buffer->buffer->subbuf_order);
if (!page)
goto free_pages;
bpage->page = page_address(page);
rb_init_page(bpage->page);
}
bpage->order = cpu_buffer->buffer->subbuf_order;
if (user_thread && fatal_signal_pending(current))
goto free_pages;
}
if (user_thread)
clear_current_oom_origin();
return 0;
free_pages:
list_for_each_entry_safe(bpage, tmp, pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
if (user_thread)
clear_current_oom_origin();
return -ENOMEM;
}
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long nr_pages)
{
LIST_HEAD(pages);
WARN_ON(!nr_pages);
if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
return -ENOMEM;
/*
* The ring buffer page list is a circular list that does not
* start and end with a list head. All page list items point to
* other pages.
*/
cpu_buffer->pages = pages.next;
list_del(&pages);
cpu_buffer->nr_pages = nr_pages;
rb_check_pages(cpu_buffer);
return 0;
}
static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_meta *meta;
struct buffer_page *bpage;
struct page *page;
int ret;
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
if (!cpu_buffer)
return NULL;
cpu_buffer->cpu = cpu;
cpu_buffer->buffer = buffer;
raw_spin_lock_init(&cpu_buffer->reader_lock);
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
init_completion(&cpu_buffer->update_done);
init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
init_waitqueue_head(&cpu_buffer->irq_work.waiters);
init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
mutex_init(&cpu_buffer->mapping_lock);
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
if (!bpage)
goto fail_free_buffer;
rb_check_bpage(cpu_buffer, bpage);
cpu_buffer->reader_page = bpage;
if (buffer->range_addr_start) {
/*
* Range mapped buffers have the same restrictions as memory
* mapped ones do.
*/
cpu_buffer->mapped = 1;
cpu_buffer->ring_meta = rb_range_meta(buffer, nr_pages, cpu);
bpage->page = rb_range_buffer(cpu_buffer, 0);
if (!bpage->page)
goto fail_free_reader;
if (cpu_buffer->ring_meta->head_buffer)
rb_meta_buffer_update(cpu_buffer, bpage);
bpage->range = 1;
} else {
page = alloc_pages_node(cpu_to_node(cpu),
GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
cpu_buffer->buffer->subbuf_order);
if (!page)
goto fail_free_reader;
bpage->page = page_address(page);
rb_init_page(bpage->page);
}
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
INIT_LIST_HEAD(&cpu_buffer->new_pages);
ret = rb_allocate_pages(cpu_buffer, nr_pages);
if (ret < 0)
goto fail_free_reader;
rb_meta_validate_events(cpu_buffer);
/* If the boot meta was valid then this has already been updated */
meta = cpu_buffer->ring_meta;
if (!meta || !meta->head_buffer ||
!cpu_buffer->head_page || !cpu_buffer->commit_page || !cpu_buffer->tail_page) {
if (meta && meta->head_buffer &&
(cpu_buffer->head_page || cpu_buffer->commit_page || cpu_buffer->tail_page)) {
pr_warn("Ring buffer meta buffers not all mapped\n");
if (!cpu_buffer->head_page)
pr_warn(" Missing head_page\n");
if (!cpu_buffer->commit_page)
pr_warn(" Missing commit_page\n");
if (!cpu_buffer->tail_page)
pr_warn(" Missing tail_page\n");
}
cpu_buffer->head_page
= list_entry(cpu_buffer->pages, struct buffer_page, list);
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
rb_head_page_activate(cpu_buffer);
if (cpu_buffer->ring_meta)
meta->commit_buffer = meta->head_buffer;
} else {
/* The valid meta buffer still needs to activate the head page */
rb_head_page_activate(cpu_buffer);
}
return cpu_buffer;
fail_free_reader:
free_buffer_page(cpu_buffer->reader_page);
fail_free_buffer:
kfree(cpu_buffer);
return NULL;
}
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
{
struct list_head *head = cpu_buffer->pages;
struct buffer_page *bpage, *tmp;
irq_work_sync(&cpu_buffer->irq_work.work);
free_buffer_page(cpu_buffer->reader_page);
if (head) {
rb_head_page_deactivate(cpu_buffer);
list_for_each_entry_safe(bpage, tmp, head, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
bpage = list_entry(head, struct buffer_page, list);
free_buffer_page(bpage);
}
free_page((unsigned long)cpu_buffer->free_page);
kfree(cpu_buffer);
}
static struct trace_buffer *alloc_buffer(unsigned long size, unsigned flags,
int order, unsigned long start,
unsigned long end,
struct lock_class_key *key)
{
struct trace_buffer *buffer;
long nr_pages;
int subbuf_size;
int bsize;
int cpu;
int ret;
/* keep it in its own cache line */
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
GFP_KERNEL);
if (!buffer)
return NULL;
if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
goto fail_free_buffer;
buffer->subbuf_order = order;
subbuf_size = (PAGE_SIZE << order);
buffer->subbuf_size = subbuf_size - BUF_PAGE_HDR_SIZE;
/* Max payload is buffer page size - header (8bytes) */
buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
buffer->flags = flags;
buffer->clock = trace_clock_local;
buffer->reader_lock_key = key;
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
init_waitqueue_head(&buffer->irq_work.waiters);
buffer->cpus = nr_cpu_ids;
bsize = sizeof(void *) * nr_cpu_ids;
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
GFP_KERNEL);
if (!buffer->buffers)
goto fail_free_cpumask;
/* If start/end are specified, then that overrides size */
if (start && end) {
unsigned long ptr;
int n;
size = end - start;
size = size / nr_cpu_ids;
/*
* The number of sub-buffers (nr_pages) is determined by the
* total size allocated minus the meta data size.
* Then that is divided by the number of per CPU buffers
* needed, plus account for the integer array index that
* will be appended to the meta data.
*/
nr_pages = (size - sizeof(struct ring_buffer_meta)) /
(subbuf_size + sizeof(int));
/* Need at least two pages plus the reader page */
if (nr_pages < 3)
goto fail_free_buffers;
again:
/* Make sure that the size fits aligned */
for (n = 0, ptr = start; n < nr_cpu_ids; n++) {
ptr += sizeof(struct ring_buffer_meta) +
sizeof(int) * nr_pages;
ptr = ALIGN(ptr, subbuf_size);
ptr += subbuf_size * nr_pages;
}
if (ptr > end) {
if (nr_pages <= 3)
goto fail_free_buffers;
nr_pages--;
goto again;
}
/* nr_pages should not count the reader page */
nr_pages--;
buffer->range_addr_start = start;
buffer->range_addr_end = end;
rb_range_meta_init(buffer, nr_pages);
} else {
/* need at least two pages */
nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
if (nr_pages < 2)
nr_pages = 2;
}
cpu = raw_smp_processor_id();
cpumask_set_cpu(cpu, buffer->cpumask);
buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
/* If already mapped, do not hook to CPU hotplug */
if (!start) {
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
if (ret < 0)
goto fail_free_buffers;
}
mutex_init(&buffer->mutex);
return buffer;
fail_free_buffers:
for_each_buffer_cpu(buffer, cpu) {
if (buffer->buffers[cpu])
rb_free_cpu_buffer(buffer->buffers[cpu]);
}
kfree(buffer->buffers);
fail_free_cpumask:
free_cpumask_var(buffer->cpumask);
fail_free_buffer:
kfree(buffer);
return NULL;
}
/**
* __ring_buffer_alloc - allocate a new ring_buffer
* @size: the size in bytes per cpu that is needed.
* @flags: attributes to set for the ring buffer.
* @key: ring buffer reader_lock_key.
*
* Currently the only flag that is available is the RB_FL_OVERWRITE
* flag. This flag means that the buffer will overwrite old data
* when the buffer wraps. If this flag is not set, the buffer will
* drop data when the tail hits the head.
*/
struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
struct lock_class_key *key)
{
/* Default buffer page size - one system page */
return alloc_buffer(size, flags, 0, 0, 0,key);
}
EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
/**
* __ring_buffer_alloc_range - allocate a new ring_buffer from existing memory
* @size: the size in bytes per cpu that is needed.
* @flags: attributes to set for the ring buffer.
* @start: start of allocated range
* @range_size: size of allocated range
* @order: sub-buffer order
* @key: ring buffer reader_lock_key.
*
* Currently the only flag that is available is the RB_FL_OVERWRITE
* flag. This flag means that the buffer will overwrite old data
* when the buffer wraps. If this flag is not set, the buffer will
* drop data when the tail hits the head.
*/
struct trace_buffer *__ring_buffer_alloc_range(unsigned long size, unsigned flags,
int order, unsigned long start,
unsigned long range_size,
struct lock_class_key *key)
{
return alloc_buffer(size, flags, order, start, start + range_size, key);
}
/**
* ring_buffer_last_boot_delta - return the delta offset from last boot
* @buffer: The buffer to return the delta from
* @text: Return text delta
* @data: Return data delta
*
* Returns: The true if the delta is non zero
*/
bool ring_buffer_last_boot_delta(struct trace_buffer *buffer, long *text,
long *data)
{
if (!buffer)
return false;
if (!buffer->last_text_delta)
return false;
*text = buffer->last_text_delta;
*data = buffer->last_data_delta;
return true;
}
/**
* ring_buffer_free - free a ring buffer.
* @buffer: the buffer to free.
*/
void
ring_buffer_free(struct trace_buffer *buffer)
{
int cpu;
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
irq_work_sync(&buffer->irq_work.work);
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
kfree(buffer->buffers);
free_cpumask_var(buffer->cpumask);
kfree(buffer);
}
EXPORT_SYMBOL_GPL(ring_buffer_free);
void ring_buffer_set_clock(struct trace_buffer *buffer,
u64 (*clock)(void))
{
buffer->clock = clock;
}
void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
{
buffer->time_stamp_abs = abs;
}
bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
{
return buffer->time_stamp_abs;
}
static inline unsigned long rb_page_entries(struct buffer_page *bpage)
{
return local_read(&bpage->entries) & RB_WRITE_MASK;
}
static inline unsigned long rb_page_write(struct buffer_page *bpage)
{
return local_read(&bpage->write) & RB_WRITE_MASK;
}
static bool
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
{
struct list_head *tail_page, *to_remove, *next_page;
struct buffer_page *to_remove_page, *tmp_iter_page;
struct buffer_page *last_page, *first_page;
unsigned long nr_removed;
unsigned long head_bit;
int page_entries;
head_bit = 0;
raw_spin_lock_irq(&cpu_buffer->reader_lock);
atomic_inc(&cpu_buffer->record_disabled);
/*
* We don't race with the readers since we have acquired the reader
* lock. We also don't race with writers after disabling recording.
* This makes it easy to figure out the first and the last page to be
* removed from the list. We unlink all the pages in between including
* the first and last pages. This is done in a busy loop so that we
* lose the least number of traces.
* The pages are freed after we restart recording and unlock readers.
*/
tail_page = &cpu_buffer->tail_page->list;
/*
* tail page might be on reader page, we remove the next page
* from the ring buffer
*/
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
tail_page = rb_list_head(tail_page->next);
to_remove = tail_page;
/* start of pages to remove */
first_page = list_entry(rb_list_head(to_remove->next),
struct buffer_page, list);
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
to_remove = rb_list_head(to_remove)->next;
head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
}
/* Read iterators need to reset themselves when some pages removed */
cpu_buffer->pages_removed += nr_removed;
next_page = rb_list_head(to_remove)->next;
/*
* Now we remove all pages between tail_page and next_page.
* Make sure that we have head_bit value preserved for the
* next page
*/
tail_page->next = (struct list_head *)((unsigned long)next_page |
head_bit);
next_page = rb_list_head(next_page);
next_page->prev = tail_page;
/* make sure pages points to a valid page in the ring buffer */
cpu_buffer->pages = next_page;
/* update head page */
if (head_bit)
cpu_buffer->head_page = list_entry(next_page,
struct buffer_page, list);
/* pages are removed, resume tracing and then free the pages */
atomic_dec(&cpu_buffer->record_disabled);
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
/* last buffer page to remove */
last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
list);
tmp_iter_page = first_page;
do {
cond_resched();
to_remove_page = tmp_iter_page;
rb_inc_page(&tmp_iter_page);
/* update the counters */
page_entries = rb_page_entries(to_remove_page);
if (page_entries) {
/*
* If something was added to this page, it was full
* since it is not the tail page. So we deduct the
* bytes consumed in ring buffer from here.
* Increment overrun to account for the lost events.
*/
local_add(page_entries, &cpu_buffer->overrun);
local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
local_inc(&cpu_buffer->pages_lost);
}
/*
* We have already removed references to this list item, just
* free up the buffer_page and its page
*/
free_buffer_page(to_remove_page);
nr_removed--;
} while (to_remove_page != last_page);
RB_WARN_ON(cpu_buffer, nr_removed);
return nr_removed == 0;
}
static bool
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
struct list_head *pages = &cpu_buffer->new_pages;
unsigned long flags;
bool success;
int retries;
/* Can be called at early boot up, where interrupts must not been enabled */
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/*
* We are holding the reader lock, so the reader page won't be swapped
* in the ring buffer. Now we are racing with the writer trying to
* move head page and the tail page.
* We are going to adapt the reader page update process where:
* 1. We first splice the start and end of list of new pages between
* the head page and its previous page.
* 2. We cmpxchg the prev_page->next to point from head page to the
* start of new pages list.
* 3. Finally, we update the head->prev to the end of new list.
*
* We will try this process 10 times, to make sure that we don't keep
* spinning.
*/
retries = 10;
success = false;
while (retries--) {
struct list_head *head_page, *prev_page;
struct list_head *last_page, *first_page;
struct list_head *head_page_with_bit;
struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
if (!hpage)
break;
head_page = &hpage->list;
prev_page = head_page->prev;
first_page = pages->next;
last_page = pages->prev;
head_page_with_bit = (struct list_head *)
((unsigned long)head_page | RB_PAGE_HEAD);
last_page->next = head_page_with_bit;
first_page->prev = prev_page;
/* caution: head_page_with_bit gets updated on cmpxchg failure */
if (try_cmpxchg(&prev_page->next,
&head_page_with_bit, first_page)) {
/*
* yay, we replaced the page pointer to our new list,
* now, we just have to update to head page's prev
* pointer to point to end of list
*/
head_page->prev = last_page;
success = true;
break;
}
}
if (success)
INIT_LIST_HEAD(pages);
/*
* If we weren't successful in adding in new pages, warn and stop
* tracing
*/
RB_WARN_ON(cpu_buffer, !success);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
/* free pages if they weren't inserted */
if (!success) {
struct buffer_page *bpage, *tmp;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
}
return success;
}
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
{
bool success;
if (cpu_buffer->nr_pages_to_update > 0)
success = rb_insert_pages(cpu_buffer);
else
success = rb_remove_pages(cpu_buffer,
-cpu_buffer->nr_pages_to_update);
if (success)
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
}
static void update_pages_handler(struct work_struct *work)
{
struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
struct ring_buffer_per_cpu, update_pages_work);
rb_update_pages(cpu_buffer);
complete(&cpu_buffer->update_done);
}
/**
* ring_buffer_resize - resize the ring buffer
* @buffer: the buffer to resize.
* @size: the new size.
* @cpu_id: the cpu buffer to resize
*
* Minimum size is 2 * buffer->subbuf_size.
*
* Returns 0 on success and < 0 on failure.
*/
int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
int cpu_id)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long nr_pages;
int cpu, err;
/*
* Always succeed at resizing a non-existent buffer:
*/
if (!buffer)
return 0;
/* Make sure the requested buffer exists */
if (cpu_id != RING_BUFFER_ALL_CPUS &&
!cpumask_test_cpu(cpu_id, buffer->cpumask))
return 0;
nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
/* we need a minimum of two pages */
if (nr_pages < 2)
nr_pages = 2;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
atomic_inc(&buffer->resizing);
if (cpu_id == RING_BUFFER_ALL_CPUS) {
/*
* Don't succeed if resizing is disabled, as a reader might be
* manipulating the ring buffer and is expecting a sane state while
* this is true.
*/
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->resize_disabled)) {
err = -EBUSY;
goto out_err_unlock;
}
}
/* calculate the pages to update */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
cpu_buffer->nr_pages_to_update = nr_pages -
cpu_buffer->nr_pages;
/*
* nothing more to do for removing pages or no update
*/
if (cpu_buffer->nr_pages_to_update <= 0)
continue;
/*
* to add pages, make sure all new pages can be
* allocated without receiving ENOMEM
*/
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
&cpu_buffer->new_pages)) {
/* not enough memory for new pages */
err = -ENOMEM;
goto out_err;
}
cond_resched();
}
cpus_read_lock();
/*
* Fire off all the required work handlers
* We can't schedule on offline CPUs, but it's not necessary
* since we can change their buffer sizes without any race.
*/
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (!cpu_buffer->nr_pages_to_update)
continue;
/* Can't run something on an offline CPU. */
if (!cpu_online(cpu)) {
rb_update_pages(cpu_buffer);
cpu_buffer->nr_pages_to_update = 0;
} else {
/* Run directly if possible. */
migrate_disable();
if (cpu != smp_processor_id()) {
migrate_enable();
schedule_work_on(cpu,
&cpu_buffer->update_pages_work);
} else {
update_pages_handler(&cpu_buffer->update_pages_work);
migrate_enable();
}
}
}
/* wait for all the updates to complete */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (!cpu_buffer->nr_pages_to_update)
continue;
if (cpu_online(cpu))
wait_for_completion(&cpu_buffer->update_done);
cpu_buffer->nr_pages_to_update = 0;
}
cpus_read_unlock();
} else {
cpu_buffer = buffer->buffers[cpu_id];
if (nr_pages == cpu_buffer->nr_pages)
goto out;
/*
* Don't succeed if resizing is disabled, as a reader might be
* manipulating the ring buffer and is expecting a sane state while
* this is true.
*/
if (atomic_read(&cpu_buffer->resize_disabled)) {
err = -EBUSY;
goto out_err_unlock;
}
cpu_buffer->nr_pages_to_update = nr_pages -
cpu_buffer->nr_pages;
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (cpu_buffer->nr_pages_to_update > 0 &&
__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
&cpu_buffer->new_pages)) {
err = -ENOMEM;
goto out_err;
}
cpus_read_lock();
/* Can't run something on an offline CPU. */
if (!cpu_online(cpu_id))
rb_update_pages(cpu_buffer);
else {
/* Run directly if possible. */
migrate_disable();
if (cpu_id == smp_processor_id()) {
rb_update_pages(cpu_buffer);
migrate_enable();
} else {
migrate_enable();
schedule_work_on(cpu_id,
&cpu_buffer->update_pages_work);
wait_for_completion(&cpu_buffer->update_done);
}
}
cpu_buffer->nr_pages_to_update = 0;
cpus_read_unlock();
}
out:
/*
* The ring buffer resize can happen with the ring buffer
* enabled, so that the update disturbs the tracing as little
* as possible. But if the buffer is disabled, we do not need
* to worry about that, and we can take the time to verify
* that the buffer is not corrupt.
*/
if (atomic_read(&buffer->record_disabled)) {
atomic_inc(&buffer->record_disabled);
/*
* Even though the buffer was disabled, we must make sure
* that it is truly disabled before calling rb_check_pages.
* There could have been a race between checking
* record_disable and incrementing it.
*/
synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) {
unsigned long flags;
cpu_buffer = buffer->buffers[cpu];
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
atomic_dec(&buffer->record_disabled);
}
atomic_dec(&buffer->resizing);
mutex_unlock(&buffer->mutex);
return 0;
out_err:
for_each_buffer_cpu(buffer, cpu) {
struct buffer_page *bpage, *tmp;
cpu_buffer = buffer->buffers[cpu];
cpu_buffer->nr_pages_to_update = 0;
if (list_empty(&cpu_buffer->new_pages))
continue;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
}
out_err_unlock:
atomic_dec(&buffer->resizing);
mutex_unlock(&buffer->mutex);
return err;
}
EXPORT_SYMBOL_GPL(ring_buffer_resize);
void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
{
mutex_lock(&buffer->mutex);
if (val)
buffer->flags |= RB_FL_OVERWRITE;
else
buffer->flags &= ~RB_FL_OVERWRITE;
mutex_unlock(&buffer->mutex);
}
EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
{
return bpage->page->data + index;
}
static __always_inline struct ring_buffer_event *
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
{
return __rb_page_index(cpu_buffer->reader_page,
cpu_buffer->reader_page->read);
}
static struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter *iter)
{
struct ring_buffer_event *event;
struct buffer_page *iter_head_page = iter->head_page;
unsigned long commit;
unsigned length;
if (iter->head != iter->next_event)
return iter->event;
/*
* When the writer goes across pages, it issues a cmpxchg which
* is a mb(), which will synchronize with the rmb here.
* (see rb_tail_page_update() and __rb_reserve_next())
*/
commit = rb_page_commit(iter_head_page);
smp_rmb();
/* An event needs to be at least 8 bytes in size */
if (iter->head > commit - 8)
goto reset;
event = __rb_page_index(iter_head_page, iter->head);
length = rb_event_length(event);
/*
* READ_ONCE() doesn't work on functions and we don't want the
* compiler doing any crazy optimizations with length.
*/
barrier();
if ((iter->head + length) > commit || length > iter->event_size)
/* Writer corrupted the read? */
goto reset;
memcpy(iter->event, event, length);
/*
* If the page stamp is still the same after this rmb() then the
* event was safely copied without the writer entering the page.
*/
smp_rmb();
/* Make sure the page didn't change since we read this */
if (iter->page_stamp != iter_head_page->page->time_stamp ||
commit > rb_page_commit(iter_head_page))
goto reset;
iter->next_event = iter->head + length;
return iter->event;
reset:
/* Reset to the beginning */
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
iter->next_event = 0;
iter->missed_events = 1;
return NULL;
}
/* Size is determined by what has been committed */
static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
{
return rb_page_commit(bpage) & ~RB_MISSED_MASK;
}
static __always_inline unsigned
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
{
return rb_page_commit(cpu_buffer->commit_page);
}
static __always_inline unsigned
rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
{
unsigned long addr = (unsigned long)event;
addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
return addr - BUF_PAGE_HDR_SIZE;
}
static void rb_inc_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/*
* The iterator could be on the reader page (it starts there).
* But the head could have moved, since the reader was
* found. Check for this case and assign the iterator
* to the head page instead of next.
*/
if (iter->head_page == cpu_buffer->reader_page)
iter->head_page = rb_set_head_page(cpu_buffer);
else
rb_inc_page(&iter->head_page);
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
iter->head = 0;
iter->next_event = 0;
}
/* Return the index into the sub-buffers for a given sub-buffer */
static int rb_meta_subbuf_idx(struct ring_buffer_meta *meta, void *subbuf)
{
void *subbuf_array;
subbuf_array = (void *)meta + sizeof(int) * meta->nr_subbufs;
subbuf_array = (void *)ALIGN((unsigned long)subbuf_array, meta->subbuf_size);
return (subbuf - subbuf_array) / meta->subbuf_size;
}
static void rb_update_meta_head(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *next_page)
{
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
unsigned long old_head = (unsigned long)next_page->page;
unsigned long new_head;
rb_inc_page(&next_page);
new_head = (unsigned long)next_page->page;
/*
* Only move it forward once, if something else came in and
* moved it forward, then we don't want to touch it.
*/
(void)cmpxchg(&meta->head_buffer, old_head, new_head);
}
static void rb_update_meta_reader(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *reader)
{
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
void *old_reader = cpu_buffer->reader_page->page;
void *new_reader = reader->page;
int id;
id = reader->id;
cpu_buffer->reader_page->id = id;
reader->id = 0;
meta->buffers[0] = rb_meta_subbuf_idx(meta, new_reader);
meta->buffers[id] = rb_meta_subbuf_idx(meta, old_reader);
/* The head pointer is the one after the reader */
rb_update_meta_head(cpu_buffer, reader);
}
/*
* rb_handle_head_page - writer hit the head page
*
* Returns: +1 to retry page
* 0 to continue
* -1 on error
*/
static int
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
struct buffer_page *tail_page,
struct buffer_page *next_page)
{
struct buffer_page *new_head;
int entries;
int type;
int ret;
entries = rb_page_entries(next_page);
/*
* The hard part is here. We need to move the head
* forward, and protect against both readers on
* other CPUs and writers coming in via interrupts.
*/
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
RB_PAGE_HEAD);
/*
* type can be one of four:
* NORMAL - an interrupt already moved it for us
* HEAD - we are the first to get here.
* UPDATE - we are the interrupt interrupting
* a current move.
* MOVED - a reader on another CPU moved the next
* pointer to its reader page. Give up
* and try again.
*/
switch (type) {
case RB_PAGE_HEAD:
/*
* We changed the head to UPDATE, thus
* it is our responsibility to update
* the counters.
*/
local_add(entries, &cpu_buffer->overrun);
local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
local_inc(&cpu_buffer->pages_lost);
if (cpu_buffer->ring_meta)
rb_update_meta_head(cpu_buffer, next_page);
/*
* The entries will be zeroed out when we move the
* tail page.
*/
/* still more to do */
break;
case RB_PAGE_UPDATE:
/*
* This is an interrupt that interrupt the
* previous update. Still more to do.
*/
break;
case RB_PAGE_NORMAL:
/*
* An interrupt came in before the update
* and processed this for us.
* Nothing left to do.
*/
return 1;
case RB_PAGE_MOVED:
/*
* The reader is on another CPU and just did
* a swap with our next_page.
* Try again.
*/
return 1;
default:
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
return -1;
}
/*
* Now that we are here, the old head pointer is
* set to UPDATE. This will keep the reader from
* swapping the head page with the reader page.
* The reader (on another CPU) will spin till
* we are finished.
*
* We just need to protect against interrupts
* doing the job. We will set the next pointer
* to HEAD. After that, we set the old pointer
* to NORMAL, but only if it was HEAD before.
* otherwise we are an interrupt, and only
* want the outer most commit to reset it.
*/
new_head = next_page;
rb_inc_page(&new_head);
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
RB_PAGE_NORMAL);
/*
* Valid returns are:
* HEAD - an interrupt came in and already set it.
* NORMAL - One of two things:
* 1) We really set it.
* 2) A bunch of interrupts came in and moved
* the page forward again.
*/
switch (ret) {
case RB_PAGE_HEAD:
case RB_PAGE_NORMAL:
/* OK */
break;
default:
RB_WARN_ON(cpu_buffer, 1);
return -1;
}
/*
* It is possible that an interrupt came in,
* set the head up, then more interrupts came in
* and moved it again. When we get back here,
* the page would have been set to NORMAL but we
* just set it back to HEAD.
*
* How do you detect this? Well, if that happened
* the tail page would have moved.
*/
if (ret == RB_PAGE_NORMAL) {
struct buffer_page *buffer_tail_page;
buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
/*
* If the tail had moved passed next, then we need
* to reset the pointer.
*/
if (buffer_tail_page != tail_page &&
buffer_tail_page != next_page)
rb_head_page_set_normal(cpu_buffer, new_head,
next_page,
RB_PAGE_HEAD);
}
/*
* If this was the outer most commit (the one that
* changed the original pointer from HEAD to UPDATE),
* then it is up to us to reset it to NORMAL.
*/
if (type == RB_PAGE_HEAD) {
ret = rb_head_page_set_normal(cpu_buffer, next_page,
tail_page,
RB_PAGE_UPDATE);
if (RB_WARN_ON(cpu_buffer,
ret != RB_PAGE_UPDATE))
return -1;
}
return 0;
}
static inline void
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long tail, struct rb_event_info *info)
{
unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
struct buffer_page *tail_page = info->tail_page;
struct ring_buffer_event *event;
unsigned long length = info->length;
/*
* Only the event that crossed the page boundary
* must fill the old tail_page with padding.
*/
if (tail >= bsize) {
/*
* If the page was filled, then we still need
* to update the real_end. Reset it to zero
* and the reader will ignore it.
*/
if (tail == bsize)
tail_page->real_end = 0;
local_sub(length, &tail_page->write);
return;
}
event = __rb_page_index(tail_page, tail);
/*
* Save the original length to the meta data.
* This will be used by the reader to add lost event
* counter.
*/
tail_page->real_end = tail;
/*
* If this event is bigger than the minimum size, then
* we need to be careful that we don't subtract the
* write counter enough to allow another writer to slip
* in on this page.
* We put in a discarded commit instead, to make sure
* that this space is not used again, and this space will
* not be accounted into 'entries_bytes'.
*
* If we are less than the minimum size, we don't need to
* worry about it.
*/
if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
/* No room for any events */
/* Mark the rest of the page with padding */
rb_event_set_padding(event);
/* Make sure the padding is visible before the write update */
smp_wmb();
/* Set the write back to the previous setting */
local_sub(length, &tail_page->write);
return;
}
/* Put in a discarded event */
event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
event->type_len = RINGBUF_TYPE_PADDING;
/* time delta must be non zero */
event->time_delta = 1;
/* account for padding bytes */
local_add(bsize - tail, &cpu_buffer->entries_bytes);
/* Make sure the padding is visible before the tail_page->write update */
smp_wmb();
/* Set write to end of buffer */
length = (tail + length) - bsize;
local_sub(length, &tail_page->write);
}
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
/*
* This is the slow path, force gcc not to inline it.
*/
static noinline struct ring_buffer_event *
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long tail, struct rb_event_info *info)
{
struct buffer_page *tail_page = info->tail_page;
struct buffer_page *commit_page = cpu_buffer->commit_page;
struct trace_buffer *buffer = cpu_buffer->buffer;
struct buffer_page *next_page;
int ret;
next_page = tail_page;
rb_inc_page(&next_page);
/*
* If for some reason, we had an interrupt storm that made
* it all the way around the buffer, bail, and warn
* about it.
*/
if (unlikely(next_page == commit_page)) {
local_inc(&cpu_buffer->commit_overrun);
goto out_reset;
}
/*
* This is where the fun begins!
*
* We are fighting against races between a reader that
* could be on another CPU trying to swap its reader
* page with the buffer head.
*
* We are also fighting against interrupts coming in and
* moving the head or tail on us as well.
*
* If the next page is the head page then we have filled
* the buffer, unless the commit page is still on the
* reader page.
*/
if (rb_is_head_page(next_page, &tail_page->list)) {
/*
* If the commit is not on the reader page, then
* move the header page.
*/
if (!rb_is_reader_page(cpu_buffer->commit_page)) {
/*
* If we are not in overwrite mode,
* this is easy, just stop here.
*/
if (!(buffer->flags & RB_FL_OVERWRITE)) {
local_inc(&cpu_buffer->dropped_events);
goto out_reset;
}
ret = rb_handle_head_page(cpu_buffer,
tail_page,
next_page);
if (ret < 0)
goto out_reset;
if (ret)
goto out_again;
} else {
/*
* We need to be careful here too. The
* commit page could still be on the reader
* page. We could have a small buffer, and
* have filled up the buffer with events
* from interrupts and such, and wrapped.
*
* Note, if the tail page is also on the
* reader_page, we let it move out.
*/
if (unlikely((cpu_buffer->commit_page !=
cpu_buffer->tail_page) &&
(cpu_buffer->commit_page ==
cpu_buffer->reader_page))) {
local_inc(&cpu_buffer->commit_overrun);
goto out_reset;
}
}
}
rb_tail_page_update(cpu_buffer, tail_page, next_page);
out_again:
rb_reset_tail(cpu_buffer, tail, info);
/* Commit what we have for now. */
rb_end_commit(cpu_buffer);
/* rb_end_commit() decs committing */
local_inc(&cpu_buffer->committing);
/* fail and let the caller try again */
return ERR_PTR(-EAGAIN);
out_reset:
/* reset write */
rb_reset_tail(cpu_buffer, tail, info);
return NULL;
}
/* Slow path */
static struct ring_buffer_event *
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event, u64 delta, bool abs)
{
if (abs)
event->type_len = RINGBUF_TYPE_TIME_STAMP;
else
event->type_len = RINGBUF_TYPE_TIME_EXTEND;
/* Not the first event on the page, or not delta? */
if (abs || rb_event_index(cpu_buffer, event)) {
event->time_delta = delta & TS_MASK;
event->array[0] = delta >> TS_SHIFT;
} else {
/* nope, just zero it */
event->time_delta = 0;
event->array[0] = 0;
}
return skip_time_extend(event);
}
#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
static inline bool sched_clock_stable(void)
{
return true;
}
#endif
static void
rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
struct rb_event_info *info)
{
u64 write_stamp;
WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
(unsigned long long)info->delta,
(unsigned long long)info->ts,
(unsigned long long)info->before,
(unsigned long long)info->after,
(unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
sched_clock_stable() ? "" :
"If you just came from a suspend/resume,\n"
"please switch to the trace global clock:\n"
" echo global > /sys/kernel/tracing/trace_clock\n"
"or add trace_clock=global to the kernel command line\n");
}
static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event **event,
struct rb_event_info *info,
u64 *delta,
unsigned int *length)
{
bool abs = info->add_timestamp &
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
if (unlikely(info->delta > (1ULL << 59))) {
/*
* Some timers can use more than 59 bits, and when a timestamp
* is added to the buffer, it will lose those bits.
*/
if (abs && (info->ts & TS_MSB)) {
info->delta &= ABS_TS_MASK;
/* did the clock go backwards */
} else if (info->before == info->after && info->before > info->ts) {
/* not interrupted */
static int once;
/*
* This is possible with a recalibrating of the TSC.
* Do not produce a call stack, but just report it.
*/
if (!once) {
once++;
pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
info->before, info->ts);
}
} else
rb_check_timestamp(cpu_buffer, info);
if (!abs)
info->delta = 0;
}
*event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
*length -= RB_LEN_TIME_EXTEND;
*delta = 0;
}
/**
* rb_update_event - update event type and data
* @cpu_buffer: The per cpu buffer of the @event
* @event: the event to update
* @info: The info to update the @event with (contains length and delta)
*
* Update the type and data fields of the @event. The length
* is the actual size that is written to the ring buffer,
* and with this, we can determine what to place into the
* data field.
*/
static void
rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event,
struct rb_event_info *info)
{
unsigned length = info->length;
u64 delta = info->delta;
unsigned int nest = local_read(&cpu_buffer->committing) - 1;
if (!WARN_ON_ONCE(nest >= MAX_NEST))
cpu_buffer->event_stamp[nest] = info->ts;
/*
* If we need to add a timestamp, then we
* add it to the start of the reserved space.
*/
if (unlikely(info->add_timestamp))
rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
event->time_delta = delta;
length -= RB_EVNT_HDR_SIZE;
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
event->type_len = 0;
event->array[0] = length;
} else
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
}
static unsigned rb_calculate_event_length(unsigned length)
{
struct ring_buffer_event event; /* Used only for sizeof array */
/* zero length can cause confusions */
if (!length)
length++;
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
length += sizeof(event.array[0]);
length += RB_EVNT_HDR_SIZE;
length = ALIGN(length, RB_ARCH_ALIGNMENT);
/*
* In case the time delta is larger than the 27 bits for it
* in the header, we need to add a timestamp. If another
* event comes in when trying to discard this one to increase
* the length, then the timestamp will be added in the allocated
* space of this event. If length is bigger than the size needed
* for the TIME_EXTEND, then padding has to be used. The events
* length must be either RB_LEN_TIME_EXTEND, or greater than or equal
* to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
* As length is a multiple of 4, we only need to worry if it
* is 12 (RB_LEN_TIME_EXTEND + 4).
*/
if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
length += RB_ALIGNMENT;
return length;
}
static inline bool
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
unsigned long new_index, old_index;
struct buffer_page *bpage;
unsigned long addr;
new_index = rb_event_index(cpu_buffer, event);
old_index = new_index + rb_event_ts_length(event);
addr = (unsigned long)event;
addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
bpage = READ_ONCE(cpu_buffer->tail_page);
/*
* Make sure the tail_page is still the same and
* the next write location is the end of this event
*/
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
unsigned long write_mask =
local_read(&bpage->write) & ~RB_WRITE_MASK;
unsigned long event_length = rb_event_length(event);
/*
* For the before_stamp to be different than the write_stamp
* to make sure that the next event adds an absolute
* value and does not rely on the saved write stamp, which
* is now going to be bogus.
*
* By setting the before_stamp to zero, the next event
* is not going to use the write_stamp and will instead
* create an absolute timestamp. This means there's no
* reason to update the wirte_stamp!
*/
rb_time_set(&cpu_buffer->before_stamp, 0);
/*
* If an event were to come in now, it would see that the
* write_stamp and the before_stamp are different, and assume
* that this event just added itself before updating
* the write stamp. The interrupting event will fix the
* write stamp for us, and use an absolute timestamp.
*/
/*
* This is on the tail page. It is possible that
* a write could come in and move the tail page
* and write to the next page. That is fine
* because we just shorten what is on this page.
*/
old_index += write_mask;
new_index += write_mask;
/* caution: old_index gets updated on cmpxchg failure */
if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
/* update counters */
local_sub(event_length, &cpu_buffer->entries_bytes);
return true;
}
}
/* could not discard */
return false;
}
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
local_inc(&cpu_buffer->committing);
local_inc(&cpu_buffer->commits);
}
static __always_inline void
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long max_count;
/*
* We only race with interrupts and NMIs on this CPU.
* If we own the commit event, then we can commit
* all others that interrupted us, since the interruptions
* are in stack format (they finish before they come
* back to us). This allows us to do a simple loop to
* assign the commit to the tail.
*/
again:
max_count = cpu_buffer->nr_pages * 100;
while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
return;
if (RB_WARN_ON(cpu_buffer,
rb_is_reader_page(cpu_buffer->tail_page)))
return;
/*
* No need for a memory barrier here, as the update
* of the tail_page did it for this page.
*/
local_set(&cpu_buffer->commit_page->page->commit,
rb_page_write(cpu_buffer->commit_page));
rb_inc_page(&cpu_buffer->commit_page);
if (cpu_buffer->ring_meta) {
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
meta->commit_buffer = (unsigned long)cpu_buffer->commit_page->page;
}
/* add barrier to keep gcc from optimizing too much */
barrier();
}
while (rb_commit_index(cpu_buffer) !=
rb_page_write(cpu_buffer->commit_page)) {
/* Make sure the readers see the content of what is committed. */
smp_wmb();
local_set(&cpu_buffer->commit_page->page->commit,
rb_page_write(cpu_buffer->commit_page));
RB_WARN_ON(cpu_buffer,
local_read(&cpu_buffer->commit_page->page->commit) &
~RB_WRITE_MASK);
barrier();
}
/* again, keep gcc from optimizing */
barrier();
/*
* If an interrupt came in just after the first while loop
* and pushed the tail page forward, we will be left with
* a dangling commit that will never go forward.
*/
if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
goto again;
}
static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long commits;
if (RB_WARN_ON(cpu_buffer,
!local_read(&cpu_buffer->committing)))
return;
again:
commits = local_read(&cpu_buffer->commits);
/* synchronize with interrupts */
barrier();
if (local_read(&cpu_buffer->committing) == 1)
rb_set_commit_to_write(cpu_buffer);
local_dec(&cpu_buffer->committing);
/* synchronize with interrupts */
barrier();
/*
* Need to account for interrupts coming in between the
* updating of the commit page and the clearing of the
* committing counter.
*/
if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
!local_read(&cpu_buffer->committing)) {
local_inc(&cpu_buffer->committing);
goto again;
}
}
static inline void rb_event_discard(struct ring_buffer_event *event)
{
if (extended_time(event))
event = skip_time_extend(event);
/* array[0] holds the actual length for the discarded event */
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
event->type_len = RINGBUF_TYPE_PADDING;
/* time delta must be non zero */
if (!event->time_delta)
event->time_delta = 1;
}
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
{
local_inc(&cpu_buffer->entries);
rb_end_commit(cpu_buffer);
}
static __always_inline void
rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
{
if (buffer->irq_work.waiters_pending) {
buffer->irq_work.waiters_pending = false;
/* irq_work_queue() supplies it's own memory barriers */
irq_work_queue(&buffer->irq_work.work);
}
if (cpu_buffer->irq_work.waiters_pending) {
cpu_buffer->irq_work.waiters_pending = false;
/* irq_work_queue() supplies it's own memory barriers */
irq_work_queue(&cpu_buffer->irq_work.work);
}
if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
return;
if (cpu_buffer->reader_page == cpu_buffer->commit_page)
return;
if (!cpu_buffer->irq_work.full_waiters_pending)
return;
cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
return;
cpu_buffer->irq_work.wakeup_full = true;
cpu_buffer->irq_work.full_waiters_pending = false;
/* irq_work_queue() supplies it's own memory barriers */
irq_work_queue(&cpu_buffer->irq_work.work);
}
#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
# define do_ring_buffer_record_recursion() \
do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
#else
# define do_ring_buffer_record_recursion() do { } while (0)
#endif
/*
* The lock and unlock are done within a preempt disable section.
* The current_context per_cpu variable can only be modified
* by the current task between lock and unlock. But it can
* be modified more than once via an interrupt. To pass this
* information from the lock to the unlock without having to
* access the 'in_interrupt()' functions again (which do show
* a bit of overhead in something as critical as function tracing,
* we use a bitmask trick.
*
* bit 1 = NMI context
* bit 2 = IRQ context
* bit 3 = SoftIRQ context
* bit 4 = normal context.
*
* This works because this is the order of contexts that can
* preempt other contexts. A SoftIRQ never preempts an IRQ
* context.
*
* When the context is determined, the corresponding bit is
* checked and set (if it was set, then a recursion of that context
* happened).
*
* On unlock, we need to clear this bit. To do so, just subtract
* 1 from the current_context and AND it to itself.
*
* (binary)
* 101 - 1 = 100
* 101 & 100 = 100 (clearing bit zero)
*
* 1010 - 1 = 1001
* 1010 & 1001 = 1000 (clearing bit 1)
*
* The least significant bit can be cleared this way, and it
* just so happens that it is the same bit corresponding to
* the current context.
*
* Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
* is set when a recursion is detected at the current context, and if
* the TRANSITION bit is already set, it will fail the recursion.
* This is needed because there's a lag between the changing of
* interrupt context and updating the preempt count. In this case,
* a false positive will be found. To handle this, one extra recursion
* is allowed, and this is done by the TRANSITION bit. If the TRANSITION
* bit is already set, then it is considered a recursion and the function
* ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
*
* On the trace_recursive_unlock(), the TRANSITION bit will be the first
* to be cleared. Even if it wasn't the context that set it. That is,
* if an interrupt comes in while NORMAL bit is set and the ring buffer
* is called before preempt_count() is updated, since the check will
* be on the NORMAL bit, the TRANSITION bit will then be set. If an
* NMI then comes in, it will set the NMI bit, but when the NMI code
* does the trace_recursive_unlock() it will clear the TRANSITION bit
* and leave the NMI bit set. But this is fine, because the interrupt
* code that set the TRANSITION bit will then clear the NMI bit when it
* calls trace_recursive_unlock(). If another NMI comes in, it will
* set the TRANSITION bit and continue.
*
* Note: The TRANSITION bit only handles a single transition between context.
*/
static __always_inline bool
trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned int val = cpu_buffer->current_context;
int bit = interrupt_context_level();
bit = RB_CTX_NORMAL - bit;
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
/*
* It is possible that this was called by transitioning
* between interrupt context, and preempt_count() has not
* been updated yet. In this case, use the TRANSITION bit.
*/
bit = RB_CTX_TRANSITION;
if (val & (1 << (bit + cpu_buffer->nest))) {
do_ring_buffer_record_recursion();
return true;
}
}
val |= (1 << (bit + cpu_buffer->nest));
cpu_buffer->current_context = val;
return false;
}
static __always_inline void
trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
{
cpu_buffer->current_context &=
cpu_buffer->current_context - (1 << cpu_buffer->nest);
}
/* The recursive locking above uses 5 bits */
#define NESTED_BITS 5
/**
* ring_buffer_nest_start - Allow to trace while nested
* @buffer: The ring buffer to modify
*
* The ring buffer has a safety mechanism to prevent recursion.
* But there may be a case where a trace needs to be done while
* tracing something else. In this case, calling this function
* will allow this function to nest within a currently active
* ring_buffer_lock_reserve().
*
* Call this function before calling another ring_buffer_lock_reserve() and
* call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
*/
void ring_buffer_nest_start(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* Enabled by ring_buffer_nest_end() */
preempt_disable_notrace();
cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
/* This is the shift value for the above recursive locking */
cpu_buffer->nest += NESTED_BITS;
}
/**
* ring_buffer_nest_end - Allow to trace while nested
* @buffer: The ring buffer to modify
*
* Must be called after ring_buffer_nest_start() and after the
* ring_buffer_unlock_commit().
*/
void ring_buffer_nest_end(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* disabled by ring_buffer_nest_start() */
cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
/* This is the shift value for the above recursive locking */
cpu_buffer->nest -= NESTED_BITS;
preempt_enable_notrace();
}
/**
* ring_buffer_unlock_commit - commit a reserved
* @buffer: The buffer to commit to
*
* This commits the data to the ring buffer, and releases any locks held.
*
* Must be paired with ring_buffer_lock_reserve.
*/
int ring_buffer_unlock_commit(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
rb_commit(cpu_buffer);
rb_wakeups(buffer, cpu_buffer);
trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
return 0;
}
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
/* Special value to validate all deltas on a page. */
#define CHECK_FULL_PAGE 1L
#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
static const char *show_irq_str(int bits)
{
const char *type[] = {
".", // 0
"s", // 1
"h", // 2
"Hs", // 3
"n", // 4
"Ns", // 5
"Nh", // 6
"NHs", // 7
};
return type[bits];
}
/* Assume this is an trace event */
static const char *show_flags(struct ring_buffer_event *event)
{
struct trace_entry *entry;
int bits = 0;
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
return "X";
entry = ring_buffer_event_data(event);
if (entry->flags & TRACE_FLAG_SOFTIRQ)
bits |= 1;
if (entry->flags & TRACE_FLAG_HARDIRQ)
bits |= 2;
if (entry->flags & TRACE_FLAG_NMI)
bits |= 4;
return show_irq_str(bits);
}
static const char *show_irq(struct ring_buffer_event *event)
{
struct trace_entry *entry;
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
return "";
entry = ring_buffer_event_data(event);
if (entry->flags & TRACE_FLAG_IRQS_OFF)
return "d";
return "";
}
static const char *show_interrupt_level(void)
{
unsigned long pc = preempt_count();
unsigned char level = 0;
if (pc & SOFTIRQ_OFFSET)
level |= 1;
if (pc & HARDIRQ_MASK)
level |= 2;
if (pc & NMI_MASK)
level |= 4;
return show_irq_str(level);
}
static void dump_buffer_page(struct buffer_data_page *bpage,
struct rb_event_info *info,
unsigned long tail)
{
struct ring_buffer_event *event;
u64 ts, delta;
int e;
ts = bpage->time_stamp;
pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
for (e = 0; e < tail; e += rb_event_length(event)) {
event = (struct ring_buffer_event *)(bpage->data + e);
switch (event->type_len) {
case RINGBUF_TYPE_TIME_EXTEND:
delta = rb_event_time_stamp(event);
ts += delta;
pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
e, ts, delta);
break;
case RINGBUF_TYPE_TIME_STAMP:
delta = rb_event_time_stamp(event);
ts = rb_fix_abs_ts(delta, ts);
pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
e, ts, delta);
break;
case RINGBUF_TYPE_PADDING:
ts += event->time_delta;
pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
e, ts, event->time_delta);
break;
case RINGBUF_TYPE_DATA:
ts += event->time_delta;
pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
e, ts, event->time_delta,
show_flags(event), show_irq(event));
break;
default:
break;
}
}
pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
}
static DEFINE_PER_CPU(atomic_t, checking);
static atomic_t ts_dump;
#define buffer_warn_return(fmt, ...) \
do { \
/* If another report is happening, ignore this one */ \
if (atomic_inc_return(&ts_dump) != 1) { \
atomic_dec(&ts_dump); \
goto out; \
} \
atomic_inc(&cpu_buffer->record_disabled); \
pr_warn(fmt, ##__VA_ARGS__); \
dump_buffer_page(bpage, info, tail); \
atomic_dec(&ts_dump); \
/* There's some cases in boot up that this can happen */ \
if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
/* Do not re-enable checking */ \
return; \
} while (0)
/*
* Check if the current event time stamp matches the deltas on
* the buffer page.
*/
static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
struct rb_event_info *info,
unsigned long tail)
{
struct buffer_data_page *bpage;
u64 ts, delta;
bool full = false;
int ret;
bpage = info->tail_page->page;
if (tail == CHECK_FULL_PAGE) {
full = true;
tail = local_read(&bpage->commit);
} else if (info->add_timestamp &
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
/* Ignore events with absolute time stamps */
return;
}
/*
* Do not check the first event (skip possible extends too).
* Also do not check if previous events have not been committed.
*/
if (tail <= 8 || tail > local_read(&bpage->commit))
return;
/*
* If this interrupted another event,
*/
if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
goto out;
ret = rb_read_data_buffer(bpage, tail, cpu_buffer->cpu, &ts, &delta);
if (ret < 0) {
if (delta < ts) {
buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
cpu_buffer->cpu, ts, delta);
goto out;
}
}
if ((full && ts > info->ts) ||
(!full && ts + info->delta != info->ts)) {
buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
cpu_buffer->cpu,
ts + info->delta, info->ts, info->delta,
info->before, info->after,
full ? " (full)" : "", show_interrupt_level());
}
out:
atomic_dec(this_cpu_ptr(&checking));
}
#else
static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
struct rb_event_info *info,
unsigned long tail)
{
}
#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
struct rb_event_info *info)
{
struct ring_buffer_event *event;
struct buffer_page *tail_page;
unsigned long tail, write, w;
/* Don't let the compiler play games with cpu_buffer->tail_page */
tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
barrier();
rb_time_read(&cpu_buffer->before_stamp, &info->before);
rb_time_read(&cpu_buffer->write_stamp, &info->after);
barrier();
info->ts = rb_time_stamp(cpu_buffer->buffer);
if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
info->delta = info->ts;
} else {
/*
* If interrupting an event time update, we may need an
* absolute timestamp.
* Don't bother if this is the start of a new page (w == 0).
*/
if (!w) {
/* Use the sub-buffer timestamp */
info->delta = 0;
} else if (unlikely(info->before != info->after)) {
info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
info->length += RB_LEN_TIME_EXTEND;
} else {
info->delta = info->ts - info->after;
if (unlikely(test_time_stamp(info->delta))) {
info->add_timestamp |= RB_ADD_STAMP_EXTEND;
info->length += RB_LEN_TIME_EXTEND;
}
}
}
/*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
/*C*/ write = local_add_return(info->length, &tail_page->write);
/* set write to only the index of the write */
write &= RB_WRITE_MASK;
tail = write - info->length;
/* See if we shot pass the end of this buffer page */
if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
return rb_move_tail(cpu_buffer, tail, info);
}
if (likely(tail == w)) {
/* Nothing interrupted us between A and C */
/*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
/*
* If something came in between C and D, the write stamp
* may now not be in sync. But that's fine as the before_stamp
* will be different and then next event will just be forced
* to use an absolute timestamp.
*/
if (likely(!(info->add_timestamp &
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
/* This did not interrupt any time update */
info->delta = info->ts - info->after;
else
/* Just use full timestamp for interrupting event */
info->delta = info->ts;
check_buffer(cpu_buffer, info, tail);
} else {
u64 ts;
/* SLOW PATH - Interrupted between A and C */
/* Save the old before_stamp */
rb_time_read(&cpu_buffer->before_stamp, &info->before);
/*
* Read a new timestamp and update the before_stamp to make
* the next event after this one force using an absolute
* timestamp. This is in case an interrupt were to come in
* between E and F.
*/
ts = rb_time_stamp(cpu_buffer->buffer);
rb_time_set(&cpu_buffer->before_stamp, ts);
barrier();
/*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
barrier();
/*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
info->after == info->before && info->after < ts) {
/*
* Nothing came after this event between C and F, it is
* safe to use info->after for the delta as it
* matched info->before and is still valid.
*/
info->delta = ts - info->after;
} else {
/*
* Interrupted between C and F:
* Lost the previous events time stamp. Just set the
* delta to zero, and this will be the same time as
* the event this event interrupted. And the events that
* came after this will still be correct (as they would
* have built their delta on the previous event.
*/
info->delta = 0;
}
info->ts = ts;
info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
}
/*
* If this is the first commit on the page, then it has the same
* timestamp as the page itself.
*/
if (unlikely(!tail && !(info->add_timestamp &
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
info->delta = 0;
/* We reserved something on the buffer */
event = __rb_page_index(tail_page, tail);
rb_update_event(cpu_buffer, event, info);
local_inc(&tail_page->entries);
/*
* If this is the first commit on the page, then update
* its timestamp.
*/
if (unlikely(!tail))
tail_page->page->time_stamp = info->ts;
/* account for these added bytes */
local_add(info->length, &cpu_buffer->entries_bytes);
return event;
}
static __always_inline struct ring_buffer_event *
rb_reserve_next_event(struct trace_buffer *buffer,
struct ring_buffer_per_cpu *cpu_buffer,
unsigned long length)
{
struct ring_buffer_event *event;
struct rb_event_info info;
int nr_loops = 0;
int add_ts_default;
/* ring buffer does cmpxchg, make sure it is safe in NMI context */
if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
(unlikely(in_nmi()))) {
return NULL;
}
rb_start_commit(cpu_buffer);
/* The commit page can not change after this */
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
/*
* Due to the ability to swap a cpu buffer from a buffer
* it is possible it was swapped before we committed.
* (committing stops a swap). We check for it here and
* if it happened, we have to fail the write.
*/
barrier();
if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
local_dec(&cpu_buffer->committing);
local_dec(&cpu_buffer->commits);
return NULL;
}
#endif
info.length = rb_calculate_event_length(length);
if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
add_ts_default = RB_ADD_STAMP_ABSOLUTE;
info.length += RB_LEN_TIME_EXTEND;
if (info.length > cpu_buffer->buffer->max_data_size)
goto out_fail;
} else {
add_ts_default = RB_ADD_STAMP_NONE;
}
again:
info.add_timestamp = add_ts_default;
info.delta = 0;
/*
* We allow for interrupts to reenter here and do a trace.
* If one does, it will cause this original code to loop
* back here. Even with heavy interrupts happening, this
* should only happen a few times in a row. If this happens
* 1000 times in a row, there must be either an interrupt
* storm or we have something buggy.
* Bail!
*/
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
goto out_fail;
event = __rb_reserve_next(cpu_buffer, &info);
if (unlikely(PTR_ERR(event) == -EAGAIN)) {
if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
info.length -= RB_LEN_TIME_EXTEND;
goto again;
}
if (likely(event))
return event;
out_fail:
rb_end_commit(cpu_buffer);
return NULL;
}
/**
* ring_buffer_lock_reserve - reserve a part of the buffer
* @buffer: the ring buffer to reserve from
* @length: the length of the data to reserve (excluding event header)
*
* Returns a reserved event on the ring buffer to copy directly to.
* The user of this interface will need to get the body to write into
* and can use the ring_buffer_event_data() interface.
*
* The length is the length of the data needed, not the event length
* which also includes the event header.
*
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
* If NULL is returned, then nothing has been allocated or locked.
*/
struct ring_buffer_event *
ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
int cpu;
/* If we are tracing schedule, we don't want to recurse */
preempt_disable_notrace();
if (unlikely(atomic_read(&buffer->record_disabled)))
goto out;
cpu = raw_smp_processor_id();
if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
goto out;
cpu_buffer = buffer->buffers[cpu];
if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
goto out;
if (unlikely(length > buffer->max_data_size))
goto out;
if (unlikely(trace_recursive_lock(cpu_buffer)))
goto out;
event = rb_reserve_next_event(buffer, cpu_buffer, length);
if (!event)
goto out_unlock;
return event;
out_unlock:
trace_recursive_unlock(cpu_buffer);
out:
preempt_enable_notrace();
return NULL;
}
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
/*
* Decrement the entries to the page that an event is on.
* The event does not even need to exist, only the pointer
* to the page it is on. This may only be called before the commit
* takes place.
*/
static inline void
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
unsigned long addr = (unsigned long)event;
struct buffer_page *bpage = cpu_buffer->commit_page;
struct buffer_page *start;
addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
/* Do the likely case first */
if (likely(bpage->page == (void *)addr)) {
local_dec(&bpage->entries);
return;
}
/*
* Because the commit page may be on the reader page we
* start with the next page and check the end loop there.
*/
rb_inc_page(&bpage);
start = bpage;
do {
if (bpage->page == (void *)addr) {
local_dec(&bpage->entries);
return;
}
rb_inc_page(&bpage);
} while (bpage != start);
/* commit not part of this buffer?? */
RB_WARN_ON(cpu_buffer, 1);
}
/**
* ring_buffer_discard_commit - discard an event that has not been committed
* @buffer: the ring buffer
* @event: non committed event to discard
*
* Sometimes an event that is in the ring buffer needs to be ignored.
* This function lets the user discard an event in the ring buffer
* and then that event will not be read later.
*
* This function only works if it is called before the item has been
* committed. It will try to free the event from the ring buffer
* if another event has not been added behind it.
*
* If another event has been added behind it, it will set the event
* up as discarded, and perform the commit.
*
* If this function is called, do not call ring_buffer_unlock_commit on
* the event.
*/
void ring_buffer_discard_commit(struct trace_buffer *buffer,
struct ring_buffer_event *event)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* The event is discarded regardless */
rb_event_discard(event);
cpu = smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
/*
* This must only be called if the event has not been
* committed yet. Thus we can assume that preemption
* is still disabled.
*/
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
rb_decrement_entry(cpu_buffer, event);
if (rb_try_to_discard(cpu_buffer, event))
goto out;
out:
rb_end_commit(cpu_buffer);
trace_recursive_unlock(cpu_buffer);
preempt_enable_notrace();
}
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
/**
* ring_buffer_write - write data to the buffer without reserving
* @buffer: The ring buffer to write to.
* @length: The length of the data being written (excluding the event header)
* @data: The data to write to the buffer.
*
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
* one function. If you already have the data to write to the buffer, it
* may be easier to simply call this function.
*
* Note, like ring_buffer_lock_reserve, the length is the length of the data
* and not the length of the event which would hold the header.
*/
int ring_buffer_write(struct trace_buffer *buffer,
unsigned long length,
void *data)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
void *body;
int ret = -EBUSY;
int cpu;
preempt_disable_notrace();
if (atomic_read(&buffer->record_disabled))
goto out;
cpu = raw_smp_processor_id();
if (!cpumask_test_cpu(cpu, buffer->cpumask))
goto out;
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled))
goto out;
if (length > buffer->max_data_size)
goto out;
if (unlikely(trace_recursive_lock(cpu_buffer)))
goto out;
event = rb_reserve_next_event(buffer, cpu_buffer, length);
if (!event)
goto out_unlock;
body = rb_event_data(event);
memcpy(body, data, length);
rb_commit(cpu_buffer);
rb_wakeups(buffer, cpu_buffer);
ret = 0;
out_unlock:
trace_recursive_unlock(cpu_buffer);
out:
preempt_enable_notrace();
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_write);
static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = cpu_buffer->reader_page;
struct buffer_page *head = rb_set_head_page(cpu_buffer);
struct buffer_page *commit = cpu_buffer->commit_page;
/* In case of error, head will be NULL */
if (unlikely(!head))
return true;
/* Reader should exhaust content in reader page */
if (reader->read != rb_page_size(reader))
return false;
/*
* If writers are committing on the reader page, knowing all
* committed content has been read, the ring buffer is empty.
*/
if (commit == reader)
return true;
/*
* If writers are committing on a page other than reader page
* and head page, there should always be content to read.
*/
if (commit != head)
return false;
/*
* Writers are committing on the head page, we just need
* to care about there're committed data, and the reader will
* swap reader page with head page when it is to read data.
*/
return rb_page_commit(commit) == 0;
}
/**
* ring_buffer_record_disable - stop all writes into the buffer
* @buffer: The ring buffer to stop writes to.
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_rcu() after this.
*/
void ring_buffer_record_disable(struct trace_buffer *buffer)
{
atomic_inc(&buffer->record_disabled);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
/**
* ring_buffer_record_enable - enable writes to the buffer
* @buffer: The ring buffer to enable writes
*
* Note, multiple disables will need the same number of enables
* to truly enable the writing (much like preempt_disable).
*/
void ring_buffer_record_enable(struct trace_buffer *buffer)
{
atomic_dec(&buffer->record_disabled);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
/**
* ring_buffer_record_off - stop all writes into the buffer
* @buffer: The ring buffer to stop writes to.
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* This is different than ring_buffer_record_disable() as
* it works like an on/off switch, where as the disable() version
* must be paired with a enable().
*/
void ring_buffer_record_off(struct trace_buffer *buffer)
{
unsigned int rd;
unsigned int new_rd;
rd = atomic_read(&buffer->record_disabled);
do {
new_rd = rd | RB_BUFFER_OFF;
} while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
}
EXPORT_SYMBOL_GPL(ring_buffer_record_off);
/**
* ring_buffer_record_on - restart writes into the buffer
* @buffer: The ring buffer to start writes to.
*
* This enables all writes to the buffer that was disabled by
* ring_buffer_record_off().
*
* This is different than ring_buffer_record_enable() as
* it works like an on/off switch, where as the enable() version
* must be paired with a disable().
*/
void ring_buffer_record_on(struct trace_buffer *buffer)
{
unsigned int rd;
unsigned int new_rd;
rd = atomic_read(&buffer->record_disabled);
do {
new_rd = rd & ~RB_BUFFER_OFF;
} while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
}
EXPORT_SYMBOL_GPL(ring_buffer_record_on);
/**
* ring_buffer_record_is_on - return true if the ring buffer can write
* @buffer: The ring buffer to see if write is enabled
*
* Returns true if the ring buffer is in a state that it accepts writes.
*/
bool ring_buffer_record_is_on(struct trace_buffer *buffer)
{
return !atomic_read(&buffer->record_disabled);
}
/**
* ring_buffer_record_is_set_on - return true if the ring buffer is set writable
* @buffer: The ring buffer to see if write is set enabled
*
* Returns true if the ring buffer is set writable by ring_buffer_record_on().
* Note that this does NOT mean it is in a writable state.
*
* It may return true when the ring buffer has been disabled by
* ring_buffer_record_disable(), as that is a temporary disabling of
* the ring buffer.
*/
bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
{
return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
}
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
* @cpu: The CPU buffer to stop
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_rcu() after this.
*/
void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->record_disabled);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
/**
* ring_buffer_record_enable_cpu - enable writes to the buffer
* @buffer: The ring buffer to enable writes
* @cpu: The CPU to enable.
*
* Note, multiple disables will need the same number of enables
* to truly enable the writing (much like preempt_disable).
*/
void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_dec(&cpu_buffer->record_disabled);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
/*
* The total entries in the ring buffer is the running counter
* of entries entered into the ring buffer, minus the sum of
* the entries read from the ring buffer and the number of
* entries that were overwritten.
*/
static inline unsigned long
rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
{
return local_read(&cpu_buffer->entries) -
(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
}
/**
* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to read from.
*/
u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
{
unsigned long flags;
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *bpage;
u64 ret = 0;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/*
* if the tail is on reader_page, oldest time stamp is on the reader
* page
*/
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
bpage = cpu_buffer->reader_page;
else
bpage = rb_set_head_page(cpu_buffer);
if (bpage)
ret = bpage->page->time_stamp;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
/**
* ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to read from.
*/
unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
/**
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the entries from.
*/
unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
return rb_num_of_entries(cpu_buffer);
}
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
/**
* ring_buffer_overrun_cpu - get the number of overruns caused by the ring
* buffer wrapping around (only if RB_FL_OVERWRITE is on).
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
ret = local_read(&cpu_buffer->overrun);
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
/**
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by
* commits failing due to the buffer wrapping around while there are uncommitted
* events, such as during an interrupt storm.
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long
ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
ret = local_read(&cpu_buffer->commit_overrun);
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
/**
* ring_buffer_dropped_events_cpu - get the number of dropped events caused by
* the ring buffer filling up (only if RB_FL_OVERWRITE is off).
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long
ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
ret = local_read(&cpu_buffer->dropped_events);
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
/**
* ring_buffer_read_events_cpu - get the number of events successfully read
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of events read
*/
unsigned long
ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
return cpu_buffer->read;
}
EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
/**
* ring_buffer_entries - get the number of entries in a buffer
* @buffer: The ring buffer
*
* Returns the total number of entries in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_entries(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long entries = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
entries += rb_num_of_entries(cpu_buffer);
}
return entries;
}
EXPORT_SYMBOL_GPL(ring_buffer_entries);
/**
* ring_buffer_overruns - get the number of overruns in buffer
* @buffer: The ring buffer
*
* Returns the total number of overruns in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long overruns = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
overruns += local_read(&cpu_buffer->overrun);
}
return overruns;
}
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
static void rb_iter_reset(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/* Iterator usage is expected to have record disabled */
iter->head_page = cpu_buffer->reader_page;
iter->head = cpu_buffer->reader_page->read;
iter->next_event = iter->head;
iter->cache_reader_page = iter->head_page;
iter->cache_read = cpu_buffer->read;
iter->cache_pages_removed = cpu_buffer->pages_removed;
if (iter->head) {
iter->read_stamp = cpu_buffer->read_stamp;
iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
} else {
iter->read_stamp = iter->head_page->page->time_stamp;
iter->page_stamp = iter->read_stamp;
}
}
/**
* ring_buffer_iter_reset - reset an iterator
* @iter: The iterator to reset
*
* Resets the iterator, so that it will start from the beginning
* again.
*/
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
if (!iter)
return;
cpu_buffer = iter->cpu_buffer;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_iter_reset(iter);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
/**
* ring_buffer_iter_empty - check if an iterator has no more to read
* @iter: The iterator to check
*/
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *reader;
struct buffer_page *head_page;
struct buffer_page *commit_page;
struct buffer_page *curr_commit_page;
unsigned commit;
u64 curr_commit_ts;
u64 commit_ts;
cpu_buffer = iter->cpu_buffer;
reader = cpu_buffer->reader_page;
head_page = cpu_buffer->head_page;
commit_page = READ_ONCE(cpu_buffer->commit_page);
commit_ts = commit_page->page->time_stamp;
/*
* When the writer goes across pages, it issues a cmpxchg which
* is a mb(), which will synchronize with the rmb here.
* (see rb_tail_page_update())
*/
smp_rmb();
commit = rb_page_commit(commit_page);
/* We want to make sure that the commit page doesn't change */
smp_rmb();
/* Make sure commit page didn't change */
curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
/* If the commit page changed, then there's more data */
if (curr_commit_page != commit_page ||
curr_commit_ts != commit_ts)
return 0;
/* Still racy, as it may return a false positive, but that's OK */
return ((iter->head_page == commit_page && iter->head >= commit) ||
(iter->head_page == reader && commit_page == head_page &&
head_page->read == commit &&
iter->head == rb_page_size(cpu_buffer->reader_page)));
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
static void
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
u64 delta;
switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = rb_event_time_stamp(event);
cpu_buffer->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
delta = rb_event_time_stamp(event);
delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
cpu_buffer->read_stamp = delta;
return;
case RINGBUF_TYPE_DATA:
cpu_buffer->read_stamp += event->time_delta;
return;
default:
RB_WARN_ON(cpu_buffer, 1);
}
}
static void
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
struct ring_buffer_event *event)
{
u64 delta;
switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = rb_event_time_stamp(event);
iter->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
delta = rb_event_time_stamp(event);
delta = rb_fix_abs_ts(delta, iter->read_stamp);
iter->read_stamp = delta;
return;
case RINGBUF_TYPE_DATA:
iter->read_stamp += event->time_delta;
return;
default:
RB_WARN_ON(iter->cpu_buffer, 1);
}
}
static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = NULL;
unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
unsigned long overwrite;
unsigned long flags;
int nr_loops = 0;
bool ret;
local_irq_save(flags);
arch_spin_lock(&cpu_buffer->lock);
again:
/*
* This should normally only loop twice. But because the
* start of the reader inserts an empty page, it causes
* a case where we will loop three times. There should be no
* reason to loop four times (that I know of).
*/
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
reader = NULL;
goto out;
}
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */
if (cpu_buffer->reader_page->read < rb_page_size(reader))
goto out;
/* Never should we have an index greater than the size */
if (RB_WARN_ON(cpu_buffer,
cpu_buffer->reader_page->read > rb_page_size(reader)))
goto out;
/* check if we caught up to the tail */
reader = NULL;
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
goto out;
/* Don't bother swapping if the ring buffer is empty */
if (rb_num_of_entries(cpu_buffer) == 0)
goto out;
/*
* Reset the reader page to size zero.
*/
local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->entries, 0);
local_set(&cpu_buffer->reader_page->page->commit, 0);
cpu_buffer->reader_page->real_end = 0;
spin:
/*
* Splice the empty reader page into the list around the head.
*/
reader = rb_set_head_page(cpu_buffer);
if (!reader)
goto out;
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
cpu_buffer->reader_page->list.prev = reader->list.prev;
/*
* cpu_buffer->pages just needs to point to the buffer, it
* has no specific buffer page to point to. Lets move it out
* of our way so we don't accidentally swap it.
*/
cpu_buffer->pages = reader->list.prev;
/* The reader page will be pointing to the new head */
rb_set_list_to_head(&cpu_buffer->reader_page->list);
/*
* We want to make sure we read the overruns after we set up our
* pointers to the next object. The writer side does a
* cmpxchg to cross pages which acts as the mb on the writer
* side. Note, the reader will constantly fail the swap
* while the writer is updating the pointers, so this
* guarantees that the overwrite recorded here is the one we
* want to compare with the last_overrun.
*/
smp_mb();
overwrite = local_read(&(cpu_buffer->overrun));
/*
* Here's the tricky part.
*
* We need to move the pointer past the header page.
* But we can only do that if a writer is not currently
* moving it. The page before the header page has the
* flag bit '1' set if it is pointing to the page we want.
* but if the writer is in the process of moving it
* than it will be '2' or already moved '0'.
*/
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
/*
* If we did not convert it, then we must try again.
*/
if (!ret)
goto spin;
if (cpu_buffer->ring_meta)
rb_update_meta_reader(cpu_buffer, reader);
/*
* Yay! We succeeded in replacing the page.
*
* Now make the new head point back to the reader page.
*/
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
rb_inc_page(&cpu_buffer->head_page);
local_inc(&cpu_buffer->pages_read);
/* Finally update the reader page to the new head */
cpu_buffer->reader_page = reader;
cpu_buffer->reader_page->read = 0;
if (overwrite != cpu_buffer->last_overrun) {
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
cpu_buffer->last_overrun = overwrite;
}
goto again;
out:
/* Update the read_stamp on the first event */
if (reader && reader->read == 0)
cpu_buffer->read_stamp = reader->page->time_stamp;
arch_spin_unlock(&cpu_buffer->lock);
local_irq_restore(flags);
/*
* The writer has preempt disable, wait for it. But not forever
* Although, 1 second is pretty much "forever"
*/
#define USECS_WAIT 1000000
for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
/* If the write is past the end of page, a writer is still updating it */
if (likely(!reader || rb_page_write(reader) <= bsize))
break;
udelay(1);
/* Get the latest version of the reader write value */
smp_rmb();
}
/* The writer is not moving forward? Something is wrong */
if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
reader = NULL;
/*
* Make sure we see any padding after the write update
* (see rb_reset_tail()).
*
* In addition, a writer may be writing on the reader page
* if the page has not been fully filled, so the read barrier
* is also needed to make sure we see the content of what is
* committed by the writer (see rb_set_commit_to_write()).
*/
smp_rmb();
return reader;
}
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
{
struct ring_buffer_event *event;
struct buffer_page *reader;
unsigned length;
reader = rb_get_reader_page(cpu_buffer);
/* This function should not be called when buffer is empty */
if (RB_WARN_ON(cpu_buffer, !reader))
return;
event = rb_reader_event(cpu_buffer);
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
cpu_buffer->read++;
rb_update_read_stamp(cpu_buffer, event);
length = rb_event_length(event);
cpu_buffer->reader_page->read += length;
cpu_buffer->read_bytes += length;
}
static void rb_advance_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
cpu_buffer = iter->cpu_buffer;
/* If head == next_event then we need to jump to the next event */
if (iter->head == iter->next_event) {
/* If the event gets overwritten again, there's nothing to do */
if (rb_iter_head_event(iter) == NULL)
return;
}
iter->head = iter->next_event;
/*
* Check if we are at the end of the buffer.
*/
if (iter->next_event >= rb_page_size(iter->head_page)) {
/* discarded commits can make the page empty */
if (iter->head_page == cpu_buffer->commit_page)
return;
rb_inc_iter(iter);
return;
}
rb_update_iter_read_stamp(iter, iter->event);
}
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
{
return cpu_buffer->lost_events;
}
static struct ring_buffer_event *
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
unsigned long *lost_events)
{
struct ring_buffer_event *event;
struct buffer_page *reader;
int nr_loops = 0;
if (ts)
*ts = 0;
again:
/*
* We repeat when a time extend is encountered.
* Since the time extend is always attached to a data event,
* we should never loop more than once.
* (We never hit the following condition more than twice).
*/
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
return NULL;
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
return NULL;
event = rb_reader_event(cpu_buffer);
switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
if (rb_null_event(event))
RB_WARN_ON(cpu_buffer, 1);
/*
* Because the writer could be discarding every
* event it creates (which would probably be bad)
* if we were to go back to "again" then we may never
* catch up, and will trigger the warn on, or lock
* the box. Return the padding, and we will release
* the current locks, and try again.
*/
return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
if (ts) {
*ts = rb_event_time_stamp(event);
*ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
cpu_buffer->cpu, ts);
}
/* Internal data, OK to advance */
rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_DATA:
if (ts && !(*ts)) {
*ts = cpu_buffer->read_stamp + event->time_delta;
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
cpu_buffer->cpu, ts);
}
if (lost_events)
*lost_events = rb_lost_events(cpu_buffer);
return event;
default:
RB_WARN_ON(cpu_buffer, 1);
}
return NULL;
}
EXPORT_SYMBOL_GPL(ring_buffer_peek);
static struct ring_buffer_event *
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
{
struct trace_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
int nr_loops = 0;
if (ts)
*ts = 0;
cpu_buffer = iter->cpu_buffer;
buffer = cpu_buffer->buffer;
/*
* Check if someone performed a consuming read to the buffer
* or removed some pages from the buffer. In these cases,
* iterator was invalidated and we need to reset it.
*/
if (unlikely(iter->cache_read != cpu_buffer->read ||
iter->cache_reader_page != cpu_buffer->reader_page ||
iter->cache_pages_removed != cpu_buffer->pages_removed))
rb_iter_reset(iter);
again:
if (ring_buffer_iter_empty(iter))
return NULL;
/*
* As the writer can mess with what the iterator is trying
* to read, just give up if we fail to get an event after
* three tries. The iterator is not as reliable when reading
* the ring buffer with an active write as the consumer is.
* Do not warn if the three failures is reached.
*/
if (++nr_loops > 3)
return NULL;
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
if (iter->head >= rb_page_size(iter->head_page)) {
rb_inc_iter(iter);
goto again;
}
event = rb_iter_head_event(iter);
if (!event)
goto again;
switch (event->type_len) {
case RINGBUF_TYPE_PADDING:
if (rb_null_event(event)) {
rb_inc_iter(iter);
goto again;
}
rb_advance_iter(iter);
return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
if (ts) {
*ts = rb_event_time_stamp(event);
*ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
cpu_buffer->cpu, ts);
}
/* Internal data, OK to advance */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_DATA:
if (ts && !(*ts)) {
*ts = iter->read_stamp + event->time_delta;
ring_buffer_normalize_time_stamp(buffer,
cpu_buffer->cpu, ts);
}
return event;
default:
RB_WARN_ON(cpu_buffer, 1);
}
return NULL;
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
{
if (likely(!in_nmi())) {
raw_spin_lock(&cpu_buffer->reader_lock);
return true;
}
/*
* If an NMI die dumps out the content of the ring buffer
* trylock must be used to prevent a deadlock if the NMI
* preempted a task that holds the ring buffer locks. If
* we get the lock then all is fine, if not, then continue
* to do the read, but this can corrupt the ring buffer,
* so it must be permanently disabled from future writes.
* Reading from NMI is a oneshot deal.
*/
if (raw_spin_trylock(&cpu_buffer->reader_lock))
return true;
/* Continue without locking, but disable the ring buffer */
atomic_inc(&cpu_buffer->record_disabled);
return false;
}
static inline void
rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
{
if (likely(locked))
raw_spin_unlock(&cpu_buffer->reader_lock);
}
/**
* ring_buffer_peek - peek at the next event to be read
* @buffer: The ring buffer to read
* @cpu: The cpu to peak at
* @ts: The timestamp counter of this event.
* @lost_events: a variable to store if events were lost (may be NULL)
*
* This will return the event that will be read next, but does
* not consume the data.
*/
struct ring_buffer_event *
ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
unsigned long *lost_events)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_event *event;
unsigned long flags;
bool dolock;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return NULL;
again:
local_irq_save(flags);
dolock = rb_reader_lock(cpu_buffer);
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
if (event && event->type_len == RINGBUF_TYPE_PADDING)
rb_advance_reader(cpu_buffer);
rb_reader_unlock(cpu_buffer, dolock);
local_irq_restore(flags);
if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
return event;
}
/** ring_buffer_iter_dropped - report if there are dropped events
* @iter: The ring buffer iterator
*
* Returns true if there was dropped events since the last peek.
*/
bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
{
bool ret = iter->missed_events != 0;
iter->missed_events = 0;
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
/**
* ring_buffer_iter_peek - peek at the next event to be read
* @iter: The ring buffer iterator
* @ts: The timestamp counter of this event.
*
* This will return the event that will be read next, but does
* not increment the iterator.
*/
struct ring_buffer_event *
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
struct ring_buffer_event *event;
unsigned long flags;
again:
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_iter_peek(iter, ts);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
return event;
}
/**
* ring_buffer_consume - return an event and consume it
* @buffer: The ring buffer to get the next event from
* @cpu: the cpu to read the buffer from
* @ts: a variable to store the timestamp (may be NULL)
* @lost_events: a variable to store if events were lost (may be NULL)
*
* Returns the next event in the ring buffer, and that event is consumed.
* Meaning, that sequential reads will keep returning a different event,
* and eventually empty the ring buffer if the producer is slower.
*/
struct ring_buffer_event *
ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
unsigned long *lost_events)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event = NULL;
unsigned long flags;
bool dolock;
again:
/* might be called in atomic */
preempt_disable();
if (!cpumask_test_cpu(cpu, buffer->cpumask))
goto out;
cpu_buffer = buffer->buffers[cpu];
local_irq_save(flags);
dolock = rb_reader_lock(cpu_buffer);
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
if (event) {
cpu_buffer->lost_events = 0;
rb_advance_reader(cpu_buffer);
}
rb_reader_unlock(cpu_buffer, dolock);
local_irq_restore(flags);
out:
preempt_enable();
if (event && event->type_len == RINGBUF_TYPE_PADDING)
goto again;
return event;
}
EXPORT_SYMBOL_GPL(ring_buffer_consume);
/**
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
* @buffer: The ring buffer to read from
* @cpu: The cpu buffer to iterate over
* @flags: gfp flags to use for memory allocation
*
* This performs the initial preparations necessary to iterate
* through the buffer. Memory is allocated, buffer resizing
* is disabled, and the iterator pointer is returned to the caller.
*
* After a sequence of ring_buffer_read_prepare calls, the user is
* expected to make at least one call to ring_buffer_read_prepare_sync.
* Afterwards, ring_buffer_read_start is invoked to get things going
* for real.
*
* This overall must be paired with ring_buffer_read_finish.
*/
struct ring_buffer_iter *
ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_iter *iter;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return NULL;
iter = kzalloc(sizeof(*iter), flags);
if (!iter)
return NULL;
/* Holds the entire event: data and meta data */
iter->event_size = buffer->subbuf_size;
iter->event = kmalloc(iter->event_size, flags);
if (!iter->event) {
kfree(iter);
return NULL;
}
cpu_buffer = buffer->buffers[cpu];
iter->cpu_buffer = cpu_buffer;
atomic_inc(&cpu_buffer->resize_disabled);
return iter;
}
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
/**
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
*
* All previously invoked ring_buffer_read_prepare calls to prepare
* iterators will be synchronized. Afterwards, read_buffer_read_start
* calls on those iterators are allowed.
*/
void
ring_buffer_read_prepare_sync(void)
{
synchronize_rcu();
}
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
/**
* ring_buffer_read_start - start a non consuming read of the buffer
* @iter: The iterator returned by ring_buffer_read_prepare
*
* This finalizes the startup of an iteration through the buffer.
* The iterator comes from a call to ring_buffer_read_prepare and
* an intervening ring_buffer_read_prepare_sync must have been
* performed.
*
* Must be paired with ring_buffer_read_finish.
*/
void
ring_buffer_read_start(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
if (!iter)
return;
cpu_buffer = iter->cpu_buffer;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
arch_spin_lock(&cpu_buffer->lock);
rb_iter_reset(iter);
arch_spin_unlock(&cpu_buffer->lock);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
/**
* ring_buffer_read_finish - finish reading the iterator of the buffer
* @iter: The iterator retrieved by ring_buffer_start
*
* This re-enables resizing of the buffer, and frees the iterator.
*/
void
ring_buffer_read_finish(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
/* Use this opportunity to check the integrity of the ring buffer. */
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_check_pages(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
atomic_dec(&cpu_buffer->resize_disabled);
kfree(iter->event);
kfree(iter);
}
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
/**
* ring_buffer_iter_advance - advance the iterator to the next location
* @iter: The ring buffer iterator
*
* Move the location of the iterator such that the next read will
* be the next location of the iterator.
*/
void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_advance_iter(iter);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
/**
* ring_buffer_size - return the size of the ring buffer (in bytes)
* @buffer: The ring buffer.
* @cpu: The CPU to get ring buffer size from.
*/
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
{
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
}
EXPORT_SYMBOL_GPL(ring_buffer_size);
/**
* ring_buffer_max_event_size - return the max data size of an event
* @buffer: The ring buffer.
*
* Returns the maximum size an event can be.
*/
unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
{
/* If abs timestamp is requested, events have a timestamp too */
if (ring_buffer_time_stamp_abs(buffer))
return buffer->max_data_size - RB_LEN_TIME_EXTEND;
return buffer->max_data_size;
}
EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
static void rb_clear_buffer_page(struct buffer_page *page)
{
local_set(&page->write, 0);
local_set(&page->entries, 0);
rb_init_page(page->page);
page->read = 0;
}
static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct trace_buffer_meta *meta = cpu_buffer->meta_page;
if (!meta)
return;
meta->reader.read = cpu_buffer->reader_page->read;
meta->reader.id = cpu_buffer->reader_page->id;
meta->reader.lost_events = cpu_buffer->lost_events;
meta->entries = local_read(&cpu_buffer->entries);
meta->overrun = local_read(&cpu_buffer->overrun);
meta->read = cpu_buffer->read;
/* Some archs do not have data cache coherency between kernel and user-space */
flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page));
}
static void
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *page;
rb_head_page_deactivate(cpu_buffer);
cpu_buffer->head_page
= list_entry(cpu_buffer->pages, struct buffer_page, list);
rb_clear_buffer_page(cpu_buffer->head_page);
list_for_each_entry(page, cpu_buffer->pages, list) {
rb_clear_buffer_page(page);
}
cpu_buffer->tail_page = cpu_buffer->head_page;
cpu_buffer->commit_page = cpu_buffer->head_page;
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
INIT_LIST_HEAD(&cpu_buffer->new_pages);
rb_clear_buffer_page(cpu_buffer->reader_page);
local_set(&cpu_buffer->entries_bytes, 0);
local_set(&cpu_buffer->overrun, 0);
local_set(&cpu_buffer->commit_overrun, 0);
local_set(&cpu_buffer->dropped_events, 0);
local_set(&cpu_buffer->entries, 0);
local_set(&cpu_buffer->committing, 0);
local_set(&cpu_buffer->commits, 0);
local_set(&cpu_buffer->pages_touched, 0);
local_set(&cpu_buffer->pages_lost, 0);
local_set(&cpu_buffer->pages_read, 0);
cpu_buffer->last_pages_touch = 0;
cpu_buffer->shortest_full = 0;
cpu_buffer->read = 0;
cpu_buffer->read_bytes = 0;
rb_time_set(&cpu_buffer->write_stamp, 0);
rb_time_set(&cpu_buffer->before_stamp, 0);
memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
cpu_buffer->lost_events = 0;
cpu_buffer->last_overrun = 0;
rb_head_page_activate(cpu_buffer);
cpu_buffer->pages_removed = 0;
if (cpu_buffer->mapped) {
rb_update_meta_page(cpu_buffer);
if (cpu_buffer->ring_meta) {
struct ring_buffer_meta *meta = cpu_buffer->ring_meta;
meta->commit_buffer = meta->head_buffer;
}
}
}
/* Must have disabled the cpu buffer then done a synchronize_rcu */
static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long flags;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
goto out;
arch_spin_lock(&cpu_buffer->lock);
rb_reset_cpu(cpu_buffer);
arch_spin_unlock(&cpu_buffer->lock);
out:
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
}
/**
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
* @buffer: The ring buffer to reset a per cpu buffer of
* @cpu: The CPU buffer to be reset
*/
void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_meta *meta;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
atomic_inc(&cpu_buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
/* Make sure all commits have finished */
synchronize_rcu();
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled);
atomic_dec(&cpu_buffer->resize_disabled);
/* Make sure persistent meta now uses this buffer's addresses */
meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
if (meta)
rb_meta_init_text_addr(meta);
mutex_unlock(&buffer->mutex);
}
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
/* Flag to ensure proper resetting of atomic variables */
#define RESET_BIT (1 << 30)
/**
* ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
* @buffer: The ring buffer to reset a per cpu buffer of
*/
void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_meta *meta;
int cpu;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
for_each_online_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
}
/* Make sure all commits have finished */
synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
/*
* If a CPU came online during the synchronize_rcu(), then
* ignore it.
*/
if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
continue;
reset_disabled_cpu_buffer(cpu_buffer);
/* Make sure persistent meta now uses this buffer's addresses */
meta = rb_range_meta(buffer, 0, cpu_buffer->cpu);
if (meta)
rb_meta_init_text_addr(meta);
atomic_dec(&cpu_buffer->record_disabled);
atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
}
mutex_unlock(&buffer->mutex);
}
/**
* ring_buffer_reset - reset a ring buffer
* @buffer: The ring buffer to reset all cpu buffers
*/
void ring_buffer_reset(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->resize_disabled);
atomic_inc(&cpu_buffer->record_disabled);
}
/* Make sure all commits have finished */
synchronize_rcu();
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
reset_disabled_cpu_buffer(cpu_buffer);
atomic_dec(&cpu_buffer->record_disabled);
atomic_dec(&cpu_buffer->resize_disabled);
}
mutex_unlock(&buffer->mutex);
}
EXPORT_SYMBOL_GPL(ring_buffer_reset);
/**
* ring_buffer_empty - is the ring buffer empty?
* @buffer: The ring buffer to test
*/
bool ring_buffer_empty(struct trace_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
bool dolock;
bool ret;
int cpu;
/* yes this is racy, but if you don't like the race, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
local_irq_save(flags);
dolock = rb_reader_lock(cpu_buffer);
ret = rb_per_cpu_empty(cpu_buffer);
rb_reader_unlock(cpu_buffer, dolock);
local_irq_restore(flags);
if (!ret)
return false;
}
return true;
}
EXPORT_SYMBOL_GPL(ring_buffer_empty);
/**
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
* @buffer: The ring buffer
* @cpu: The CPU buffer to test
*/
bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
bool dolock;
bool ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return true;
cpu_buffer = buffer->buffers[cpu];
local_irq_save(flags);
dolock = rb_reader_lock(cpu_buffer);
ret = rb_per_cpu_empty(cpu_buffer);
rb_reader_unlock(cpu_buffer, dolock);
local_irq_restore(flags);
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
/**
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
* @buffer_a: One buffer to swap with
* @buffer_b: The other buffer to swap with
* @cpu: the CPU of the buffers to swap
*
* This function is useful for tracers that want to take a "snapshot"
* of a CPU buffer and has another back up buffer lying around.
* it is expected that the tracer handles the cpu buffer not being
* used at the moment.
*/
int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
struct trace_buffer *buffer_b, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
int ret = -EINVAL;
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
!cpumask_test_cpu(cpu, buffer_b->cpumask))
goto out;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
/* It's up to the callers to not try to swap mapped buffers */
if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
ret = -EBUSY;
goto out;
}
/* At least make sure the two buffers are somewhat the same */
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
goto out;
if (buffer_a->subbuf_order != buffer_b->subbuf_order)
goto out;
ret = -EAGAIN;
if (atomic_read(&buffer_a->record_disabled))
goto out;
if (atomic_read(&buffer_b->record_disabled))
goto out;
if (atomic_read(&cpu_buffer_a->record_disabled))
goto out;
if (atomic_read(&cpu_buffer_b->record_disabled))
goto out;
/*
* We can't do a synchronize_rcu here because this
* function can be called in atomic context.
* Normally this will be called from the same CPU as cpu.
* If not it's up to the caller to protect this.
*/
atomic_inc(&cpu_buffer_a->record_disabled);
atomic_inc(&cpu_buffer_b->record_disabled);
ret = -EBUSY;
if (local_read(&cpu_buffer_a->committing))
goto out_dec;
if (local_read(&cpu_buffer_b->committing))
goto out_dec;
/*
* When resize is in progress, we cannot swap it because
* it will mess the state of the cpu buffer.
*/
if (atomic_read(&buffer_a->resizing))
goto out_dec;
if (atomic_read(&buffer_b->resizing))
goto out_dec;
buffer_a->buffers[cpu] = cpu_buffer_b;
buffer_b->buffers[cpu] = cpu_buffer_a;
cpu_buffer_b->buffer = buffer_a;
cpu_buffer_a->buffer = buffer_b;
ret = 0;
out_dec:
atomic_dec(&cpu_buffer_a->record_disabled);
atomic_dec(&cpu_buffer_b->record_disabled);
out:
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
/**
* ring_buffer_alloc_read_page - allocate a page to read from buffer
* @buffer: the buffer to allocate for.
* @cpu: the cpu buffer to allocate.
*
* This function is used in conjunction with ring_buffer_read_page.
* When reading a full page from the ring buffer, these functions
* can be used to speed up the process. The calling function should
* allocate a few pages first with this function. Then when it
* needs to get pages from the ring buffer, it passes the result
* of this function into ring_buffer_read_page, which will swap
* the page that was allocated, with the read page of the buffer.
*
* Returns:
* The page allocated, or ERR_PTR
*/
struct buffer_data_read_page *
ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_data_read_page *bpage = NULL;
unsigned long flags;
struct page *page;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return ERR_PTR(-ENODEV);
bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
if (!bpage)
return ERR_PTR(-ENOMEM);
bpage->order = buffer->subbuf_order;
cpu_buffer = buffer->buffers[cpu];
local_irq_save(flags);
arch_spin_lock(&cpu_buffer->lock);
if (cpu_buffer->free_page) {
bpage->data = cpu_buffer->free_page;
cpu_buffer->free_page = NULL;
}
arch_spin_unlock(&cpu_buffer->lock);
local_irq_restore(flags);
if (bpage->data)
goto out;
page = alloc_pages_node(cpu_to_node(cpu),
GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
cpu_buffer->buffer->subbuf_order);
if (!page) {
kfree(bpage);
return ERR_PTR(-ENOMEM);
}
bpage->data = page_address(page);
out:
rb_init_page(bpage->data);
return bpage;
}
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
/**
* ring_buffer_free_read_page - free an allocated read page
* @buffer: the buffer the page was allocate for
* @cpu: the cpu buffer the page came from
* @data_page: the page to free
*
* Free a page allocated from ring_buffer_alloc_read_page.
*/
void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
struct buffer_data_read_page *data_page)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_data_page *bpage = data_page->data;
struct page *page = virt_to_page(bpage);
unsigned long flags;
if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
return;
cpu_buffer = buffer->buffers[cpu];
/*
* If the page is still in use someplace else, or order of the page
* is different from the subbuffer order of the buffer -
* we can't reuse it
*/
if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
goto out;
local_irq_save(flags);
arch_spin_lock(&cpu_buffer->lock);
if (!cpu_buffer->free_page) {
cpu_buffer->free_page = bpage;
bpage = NULL;
}
arch_spin_unlock(&cpu_buffer->lock);
local_irq_restore(flags);
out:
free_pages((unsigned long)bpage, data_page->order);
kfree(data_page);
}
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
/**
* ring_buffer_read_page - extract a page from the ring buffer
* @buffer: buffer to extract from
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
* @len: amount to extract
* @cpu: the cpu of the buffer to extract
* @full: should the extraction only happen when the page is full.
*
* This function will pull out a page from the ring buffer and consume it.
* @data_page must be the address of the variable that was returned
* from ring_buffer_alloc_read_page. This is because the page might be used
* to swap with a page in the ring buffer.
*
* for example:
* rpage = ring_buffer_alloc_read_page(buffer, cpu);
* if (IS_ERR(rpage))
* return PTR_ERR(rpage);
* ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
* if (ret >= 0)
* process_page(ring_buffer_read_page_data(rpage), ret);
* ring_buffer_free_read_page(buffer, cpu, rpage);
*
* When @full is set, the function will not return true unless
* the writer is off the reader page.
*
* Note: it is up to the calling functions to handle sleeps and wakeups.
* The ring buffer can be used anywhere in the kernel and can not
* blindly call wake_up. The layer that uses the ring buffer must be
* responsible for that.
*
* Returns:
* >=0 if data has been transferred, returns the offset of consumed data.
* <0 if no data has been transferred.
*/
int ring_buffer_read_page(struct trace_buffer *buffer,
struct buffer_data_read_page *data_page,
size_t len, int cpu, int full)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_event *event;
struct buffer_data_page *bpage;
struct buffer_page *reader;
unsigned long missed_events;
unsigned long flags;
unsigned int commit;
unsigned int read;
u64 save_timestamp;
int ret = -1;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
goto out;
/*
* If len is not big enough to hold the page header, then
* we can not copy anything.
*/
if (len <= BUF_PAGE_HDR_SIZE)
goto out;
len -= BUF_PAGE_HDR_SIZE;
if (!data_page || !data_page->data)
goto out;
if (data_page->order != buffer->subbuf_order)
goto out;
bpage = data_page->data;
if (!bpage)
goto out;
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
goto out_unlock;
event = rb_reader_event(cpu_buffer);
read = reader->read;
commit = rb_page_size(reader);
/* Check if any events were dropped */
missed_events = cpu_buffer->lost_events;
/*
* If this page has been partially read or
* if len is not big enough to read the rest of the page or
* a writer is still on the page, then
* we must copy the data from the page to the buffer.
* Otherwise, we can simply swap the page with the one passed in.
*/
if (read || (len < (commit - read)) ||
cpu_buffer->reader_page == cpu_buffer->commit_page ||
cpu_buffer->mapped) {
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
unsigned int rpos = read;
unsigned int pos = 0;
unsigned int size;
/*
* If a full page is expected, this can still be returned
* if there's been a previous partial read and the
* rest of the page can be read and the commit page is off
* the reader page.
*/
if (full &&
(!read || (len < (commit - read)) ||
cpu_buffer->reader_page == cpu_buffer->commit_page))
goto out_unlock;
if (len > (commit - read))
len = (commit - read);
/* Always keep the time extend and data together */
size = rb_event_ts_length(event);
if (len < size)
goto out_unlock;
/* save the current timestamp, since the user will need it */
save_timestamp = cpu_buffer->read_stamp;
/* Need to copy one event at a time */
do {
/* We need the size of one event, because
* rb_advance_reader only advances by one event,
* whereas rb_event_ts_length may include the size of
* one or two events.
* We have already ensured there's enough space if this
* is a time extend. */
size = rb_event_length(event);
memcpy(bpage->data + pos, rpage->data + rpos, size);
len -= size;
rb_advance_reader(cpu_buffer);
rpos = reader->read;
pos += size;
if (rpos >= commit)
break;
event = rb_reader_event(cpu_buffer);
/* Always keep the time extend and data together */
size = rb_event_ts_length(event);
} while (len >= size);
/* update bpage */
local_set(&bpage->commit, pos);
bpage->time_stamp = save_timestamp;
/* we copied everything to the beginning */
read = 0;
} else {
/* update the entry counter */
cpu_buffer->read += rb_page_entries(reader);
cpu_buffer->read_bytes += rb_page_size(reader);
/* swap the pages */
rb_init_page(bpage);
bpage = reader->page;
reader->page = data_page->data;
local_set(&reader->write, 0);
local_set(&reader->entries, 0);
reader->read = 0;
data_page->data = bpage;
/*
* Use the real_end for the data size,
* This gives us a chance to store the lost events
* on the page.
*/
if (reader->real_end)
local_set(&bpage->commit, reader->real_end);
}
ret = read;
cpu_buffer->lost_events = 0;
commit = local_read(&bpage->commit);
/*
* Set a flag in the commit field if we lost events
*/
if (missed_events) {
/* If there is room at the end of the page to save the
* missed events, then record it there.
*/
if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
memcpy(&bpage->data[commit], &missed_events,
sizeof(missed_events));
local_add(RB_MISSED_STORED, &bpage->commit);
commit += sizeof(missed_events);
}
local_add(RB_MISSED_EVENTS, &bpage->commit);
}
/*
* This page may be off to user land. Zero it out here.
*/
if (commit < buffer->subbuf_size)
memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
out_unlock:
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
out:
return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
/**
* ring_buffer_read_page_data - get pointer to the data in the page.
* @page: the page to get the data from
*
* Returns pointer to the actual data in this page.
*/
void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
{
return page->data;
}
EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
/**
* ring_buffer_subbuf_size_get - get size of the sub buffer.
* @buffer: the buffer to get the sub buffer size from
*
* Returns size of the sub buffer, in bytes.
*/
int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
{
return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
}
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
/**
* ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
* @buffer: The ring_buffer to get the system sub page order from
*
* By default, one ring buffer sub page equals to one system page. This parameter
* is configurable, per ring buffer. The size of the ring buffer sub page can be
* extended, but must be an order of system page size.
*
* Returns the order of buffer sub page size, in system pages:
* 0 means the sub buffer size is 1 system page and so forth.
* In case of an error < 0 is returned.
*/
int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
{
if (!buffer)
return -EINVAL;
return buffer->subbuf_order;
}
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
/**
* ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
* @buffer: The ring_buffer to set the new page size.
* @order: Order of the system pages in one sub buffer page
*
* By default, one ring buffer pages equals to one system page. This API can be
* used to set new size of the ring buffer page. The size must be order of
* system page size, that's why the input parameter @order is the order of
* system pages that are allocated for one ring buffer page:
* 0 - 1 system page
* 1 - 2 system pages
* 3 - 4 system pages
* ...
*
* Returns 0 on success or < 0 in case of an error.
*/
int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *bpage, *tmp;
int old_order, old_size;
int nr_pages;
int psize;
int err;
int cpu;
if (!buffer || order < 0)
return -EINVAL;
if (buffer->subbuf_order == order)
return 0;
psize = (1 << order) * PAGE_SIZE;
if (psize <= BUF_PAGE_HDR_SIZE)
return -EINVAL;
/* Size of a subbuf cannot be greater than the write counter */
if (psize > RB_WRITE_MASK + 1)
return -EINVAL;
old_order = buffer->subbuf_order;
old_size = buffer->subbuf_size;
/* prevent another thread from changing buffer sizes */
mutex_lock(&buffer->mutex);
atomic_inc(&buffer->record_disabled);
/* Make sure all commits have finished */
synchronize_rcu();
buffer->subbuf_order = order;
buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
/* Make sure all new buffers are allocated, before deleting the old ones */
for_each_buffer_cpu(buffer, cpu) {
if (!cpumask_test_cpu(cpu, buffer->cpumask))
continue;
cpu_buffer = buffer->buffers[cpu];
if (cpu_buffer->mapped) {
err = -EBUSY;
goto error;
}
/* Update the number of pages to match the new size */
nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
/* we need a minimum of two pages */
if (nr_pages < 2)
nr_pages = 2;
cpu_buffer->nr_pages_to_update = nr_pages;
/* Include the reader page */
nr_pages++;
/* Allocate the new size buffer */
INIT_LIST_HEAD(&cpu_buffer->new_pages);
if (__rb_allocate_pages(cpu_buffer, nr_pages,
&cpu_buffer->new_pages)) {
/* not enough memory for new pages */
err = -ENOMEM;
goto error;
}
}
for_each_buffer_cpu(buffer, cpu) {
struct buffer_data_page *old_free_data_page;
struct list_head old_pages;
unsigned long flags;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
continue;
cpu_buffer = buffer->buffers[cpu];
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* Clear the head bit to make the link list normal to read */
rb_head_page_deactivate(cpu_buffer);
/*
* Collect buffers from the cpu_buffer pages list and the
* reader_page on old_pages, so they can be freed later when not
* under a spinlock. The pages list is a linked list with no
* head, adding old_pages turns it into a regular list with
* old_pages being the head.
*/
list_add(&old_pages, cpu_buffer->pages);
list_add(&cpu_buffer->reader_page->list, &old_pages);
/* One page was allocated for the reader page */
cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
struct buffer_page, list);
list_del_init(&cpu_buffer->reader_page->list);
/* Install the new pages, remove the head from the list */
cpu_buffer->pages = cpu_buffer->new_pages.next;
list_del_init(&cpu_buffer->new_pages);
cpu_buffer->head_page
= list_entry(cpu_buffer->pages, struct buffer_page, list);
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
cpu_buffer->nr_pages_to_update = 0;
old_free_data_page = cpu_buffer->free_page;
cpu_buffer->free_page = NULL;
rb_head_page_activate(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
/* Free old sub buffers */
list_for_each_entry_safe(bpage, tmp, &old_pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
free_pages((unsigned long)old_free_data_page, old_order);
rb_check_pages(cpu_buffer);
}
atomic_dec(&buffer->record_disabled);
mutex_unlock(&buffer->mutex);
return 0;
error:
buffer->subbuf_order = old_order;
buffer->subbuf_size = old_size;
atomic_dec(&buffer->record_disabled);
mutex_unlock(&buffer->mutex);
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (!cpu_buffer->nr_pages_to_update)
continue;
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
}
return err;
}
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct page *page;
if (cpu_buffer->meta_page)
return 0;
page = alloc_page(GFP_USER | __GFP_ZERO);
if (!page)
return -ENOMEM;
cpu_buffer->meta_page = page_to_virt(page);
return 0;
}
static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
{
unsigned long addr = (unsigned long)cpu_buffer->meta_page;
free_page(addr);
cpu_buffer->meta_page = NULL;
}
static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer,
unsigned long *subbuf_ids)
{
struct trace_buffer_meta *meta = cpu_buffer->meta_page;
unsigned int nr_subbufs = cpu_buffer->nr_pages + 1;
struct buffer_page *first_subbuf, *subbuf;
int id = 0;
subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page;
cpu_buffer->reader_page->id = id++;
first_subbuf = subbuf = rb_set_head_page(cpu_buffer);
do {
if (WARN_ON(id >= nr_subbufs))
break;
subbuf_ids[id] = (unsigned long)subbuf->page;
subbuf->id = id;
rb_inc_page(&subbuf);
id++;
} while (subbuf != first_subbuf);
/* install subbuf ID to kern VA translation */
cpu_buffer->subbuf_ids = subbuf_ids;
meta->meta_struct_len = sizeof(*meta);
meta->nr_subbufs = nr_subbufs;
meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
meta->meta_page_size = meta->subbuf_size;
rb_update_meta_page(cpu_buffer);
}
static struct ring_buffer_per_cpu *
rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return ERR_PTR(-EINVAL);
cpu_buffer = buffer->buffers[cpu];
mutex_lock(&cpu_buffer->mapping_lock);
if (!cpu_buffer->user_mapped) {
mutex_unlock(&cpu_buffer->mapping_lock);
return ERR_PTR(-ENODEV);
}
return cpu_buffer;
}
static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer)
{
mutex_unlock(&cpu_buffer->mapping_lock);
}
/*
* Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need
* to be set-up or torn-down.
*/
static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
bool inc)
{
unsigned long flags;
lockdep_assert_held(&cpu_buffer->mapping_lock);
/* mapped is always greater or equal to user_mapped */
if (WARN_ON(cpu_buffer->mapped < cpu_buffer->user_mapped))
return -EINVAL;
if (inc && cpu_buffer->mapped == UINT_MAX)
return -EBUSY;
if (WARN_ON(!inc && cpu_buffer->user_mapped == 0))
return -EINVAL;
mutex_lock(&cpu_buffer->buffer->mutex);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
if (inc) {
cpu_buffer->user_mapped++;
cpu_buffer->mapped++;
} else {
cpu_buffer->user_mapped--;
cpu_buffer->mapped--;
}
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
mutex_unlock(&cpu_buffer->buffer->mutex);
return 0;
}
/*
* +--------------+ pgoff == 0
* | meta page |
* +--------------+ pgoff == 1
* | subbuffer 0 |
* | |
* +--------------+ pgoff == (1 + (1 << subbuf_order))
* | subbuffer 1 |
* | |
* ...
*/
#ifdef CONFIG_MMU
static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
struct vm_area_struct *vma)
{
unsigned long nr_subbufs, nr_pages, nr_vma_pages, pgoff = vma->vm_pgoff;
unsigned int subbuf_pages, subbuf_order;
struct page **pages;
int p = 0, s = 0;
int err;
/* Refuse MP_PRIVATE or writable mappings */
if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
!(vma->vm_flags & VM_MAYSHARE))
return -EPERM;
subbuf_order = cpu_buffer->buffer->subbuf_order;
subbuf_pages = 1 << subbuf_order;
if (subbuf_order && pgoff % subbuf_pages)
return -EINVAL;
/*
* Make sure the mapping cannot become writable later. Also tell the VM
* to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
*/
vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
VM_MAYWRITE);
lockdep_assert_held(&cpu_buffer->mapping_lock);
nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
nr_pages = ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */
nr_vma_pages = vma_pages(vma);
if (!nr_vma_pages || nr_vma_pages > nr_pages)
return -EINVAL;
nr_pages = nr_vma_pages;
pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
if (!pages)
return -ENOMEM;
if (!pgoff) {
unsigned long meta_page_padding;
pages[p++] = virt_to_page(cpu_buffer->meta_page);
/*
* Pad with the zero-page to align the meta-page with the
* sub-buffers.
*/
meta_page_padding = subbuf_pages - 1;
while (meta_page_padding-- && p < nr_pages) {
unsigned long __maybe_unused zero_addr =
vma->vm_start + (PAGE_SIZE * p);
pages[p++] = ZERO_PAGE(zero_addr);
}
} else {
/* Skip the meta-page */
pgoff -= subbuf_pages;
s += pgoff / subbuf_pages;
}
while (p < nr_pages) {
struct page *page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
int off = 0;
if (WARN_ON_ONCE(s >= nr_subbufs)) {
err = -EINVAL;
goto out;
}
for (; off < (1 << (subbuf_order)); off++, page++) {
if (p >= nr_pages)
break;
pages[p++] = page;
}
s++;
}
err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
out:
kfree(pages);
return err;
}
#else
static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
struct vm_area_struct *vma)
{
return -EOPNOTSUPP;
}
#endif
int ring_buffer_map(struct trace_buffer *buffer, int cpu,
struct vm_area_struct *vma)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags, *subbuf_ids;
int err = 0;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return -EINVAL;
cpu_buffer = buffer->buffers[cpu];
mutex_lock(&cpu_buffer->mapping_lock);
if (cpu_buffer->user_mapped) {
err = __rb_map_vma(cpu_buffer, vma);
if (!err)
err = __rb_inc_dec_mapped(cpu_buffer, true);
mutex_unlock(&cpu_buffer->mapping_lock);
return err;
}
/* prevent another thread from changing buffer/sub-buffer sizes */
mutex_lock(&buffer->mutex);
err = rb_alloc_meta_page(cpu_buffer);
if (err)
goto unlock;
/* subbuf_ids include the reader while nr_pages does not */
subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL);
if (!subbuf_ids) {
rb_free_meta_page(cpu_buffer);
err = -ENOMEM;
goto unlock;
}
atomic_inc(&cpu_buffer->resize_disabled);
/*
* Lock all readers to block any subbuf swap until the subbuf IDs are
* assigned.
*/
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
err = __rb_map_vma(cpu_buffer, vma);
if (!err) {
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* This is the first time it is mapped by user */
cpu_buffer->mapped++;
cpu_buffer->user_mapped = 1;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
} else {
kfree(cpu_buffer->subbuf_ids);
cpu_buffer->subbuf_ids = NULL;
rb_free_meta_page(cpu_buffer);
}
unlock:
mutex_unlock(&buffer->mutex);
mutex_unlock(&cpu_buffer->mapping_lock);
return err;
}
int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
int err = 0;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return -EINVAL;
cpu_buffer = buffer->buffers[cpu];
mutex_lock(&cpu_buffer->mapping_lock);
if (!cpu_buffer->user_mapped) {
err = -ENODEV;
goto out;
} else if (cpu_buffer->user_mapped > 1) {
__rb_inc_dec_mapped(cpu_buffer, false);
goto out;
}
mutex_lock(&buffer->mutex);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
/* This is the last user space mapping */
if (!WARN_ON_ONCE(cpu_buffer->mapped < cpu_buffer->user_mapped))
cpu_buffer->mapped--;
cpu_buffer->user_mapped = 0;
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
kfree(cpu_buffer->subbuf_ids);
cpu_buffer->subbuf_ids = NULL;
rb_free_meta_page(cpu_buffer);
atomic_dec(&cpu_buffer->resize_disabled);
mutex_unlock(&buffer->mutex);
out:
mutex_unlock(&cpu_buffer->mapping_lock);
return err;
}
int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct buffer_page *reader;
unsigned long missed_events;
unsigned long reader_size;
unsigned long flags;
cpu_buffer = rb_get_mapped_buffer(buffer, cpu);
if (IS_ERR(cpu_buffer))
return (int)PTR_ERR(cpu_buffer);
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
consume:
if (rb_per_cpu_empty(cpu_buffer))
goto out;
reader_size = rb_page_size(cpu_buffer->reader_page);
/*
* There are data to be read on the current reader page, we can
* return to the caller. But before that, we assume the latter will read
* everything. Let's update the kernel reader accordingly.
*/
if (cpu_buffer->reader_page->read < reader_size) {
while (cpu_buffer->reader_page->read < reader_size)
rb_advance_reader(cpu_buffer);
goto out;
}
reader = rb_get_reader_page(cpu_buffer);
if (WARN_ON(!reader))
goto out;
/* Check if any events were dropped */
missed_events = cpu_buffer->lost_events;
if (cpu_buffer->reader_page != cpu_buffer->commit_page) {
if (missed_events) {
struct buffer_data_page *bpage = reader->page;
unsigned int commit;
/*
* Use the real_end for the data size,
* This gives us a chance to store the lost events
* on the page.
*/
if (reader->real_end)
local_set(&bpage->commit, reader->real_end);
/*
* If there is room at the end of the page to save the
* missed events, then record it there.
*/
commit = rb_page_size(reader);
if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
memcpy(&bpage->data[commit], &missed_events,
sizeof(missed_events));
local_add(RB_MISSED_STORED, &bpage->commit);
}
local_add(RB_MISSED_EVENTS, &bpage->commit);
}
} else {
/*
* There really shouldn't be any missed events if the commit
* is on the reader page.
*/
WARN_ON_ONCE(missed_events);
}
cpu_buffer->lost_events = 0;
goto consume;
out:
/* Some archs do not have data cache coherency between kernel and user-space */
flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page));
rb_update_meta_page(cpu_buffer);
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
rb_put_mapped_buffer(cpu_buffer);
return 0;
}
/*
* We only allocate new buffers, never free them if the CPU goes down.
* If we were to free the buffer, then the user would lose any trace that was in
* the buffer.
*/
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
{
struct trace_buffer *buffer;
long nr_pages_same;
int cpu_i;
unsigned long nr_pages;
buffer = container_of(node, struct trace_buffer, node);
if (cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
nr_pages = 0;
nr_pages_same = 1;
/* check if all cpu sizes are same */
for_each_buffer_cpu(buffer, cpu_i) {
/* fill in the size from first enabled cpu */
if (nr_pages == 0)
nr_pages = buffer->buffers[cpu_i]->nr_pages;
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
nr_pages_same = 0;
break;
}
}
/* allocate minimum pages, user can later expand it */
if (!nr_pages_same)
nr_pages = 2;
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
if (!buffer->buffers[cpu]) {
WARN(1, "failed to allocate ring buffer on CPU %u\n",
cpu);
return -ENOMEM;
}
smp_wmb();
cpumask_set_cpu(cpu, buffer->cpumask);
return 0;
}
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
/*
* This is a basic integrity check of the ring buffer.
* Late in the boot cycle this test will run when configured in.
* It will kick off a thread per CPU that will go into a loop
* writing to the per cpu ring buffer various sizes of data.
* Some of the data will be large items, some small.
*
* Another thread is created that goes into a spin, sending out
* IPIs to the other CPUs to also write into the ring buffer.
* this is to test the nesting ability of the buffer.
*
* Basic stats are recorded and reported. If something in the
* ring buffer should happen that's not expected, a big warning
* is displayed and all ring buffers are disabled.
*/
static struct task_struct *rb_threads[NR_CPUS] __initdata;
struct rb_test_data {
struct trace_buffer *buffer;
unsigned long events;
unsigned long bytes_written;
unsigned long bytes_alloc;
unsigned long bytes_dropped;
unsigned long events_nested;
unsigned long bytes_written_nested;
unsigned long bytes_alloc_nested;
unsigned long bytes_dropped_nested;
int min_size_nested;
int max_size_nested;
int max_size;
int min_size;
int cpu;
int cnt;
};
static struct rb_test_data rb_data[NR_CPUS] __initdata;
/* 1 meg per cpu */
#define RB_TEST_BUFFER_SIZE 1048576
static char rb_string[] __initdata =
"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
static bool rb_test_started __initdata;
struct rb_item {
int size;
char str[];
};
static __init int rb_write_something(struct rb_test_data *data, bool nested)
{
struct ring_buffer_event *event;
struct rb_item *item;
bool started;
int event_len;
int size;
int len;
int cnt;
/* Have nested writes different that what is written */
cnt = data->cnt + (nested ? 27 : 0);
/* Multiply cnt by ~e, to make some unique increment */
size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
len = size + sizeof(struct rb_item);
started = rb_test_started;
/* read rb_test_started before checking buffer enabled */
smp_rmb();
event = ring_buffer_lock_reserve(data->buffer, len);
if (!event) {
/* Ignore dropped events before test starts. */
if (started) {
if (nested)
data->bytes_dropped += len;
else
data->bytes_dropped_nested += len;
}
return len;
}
event_len = ring_buffer_event_length(event);
if (RB_WARN_ON(data->buffer, event_len < len))
goto out;
item = ring_buffer_event_data(event);
item->size = size;
memcpy(item->str, rb_string, size);
if (nested) {
data->bytes_alloc_nested += event_len;
data->bytes_written_nested += len;
data->events_nested++;
if (!data->min_size_nested || len < data->min_size_nested)
data->min_size_nested = len;
if (len > data->max_size_nested)
data->max_size_nested = len;
} else {
data->bytes_alloc += event_len;
data->bytes_written += len;
data->events++;
if (!data->min_size || len < data->min_size)
data->max_size = len;
if (len > data->max_size)
data->max_size = len;
}
out:
ring_buffer_unlock_commit(data->buffer);
return 0;
}
static __init int rb_test(void *arg)
{
struct rb_test_data *data = arg;
while (!kthread_should_stop()) {
rb_write_something(data, false);
data->cnt++;
set_current_state(TASK_INTERRUPTIBLE);
/* Now sleep between a min of 100-300us and a max of 1ms */
usleep_range(((data->cnt % 3) + 1) * 100, 1000);
}
return 0;
}
static __init void rb_ipi(void *ignore)
{
struct rb_test_data *data;
int cpu = smp_processor_id();
data = &rb_data[cpu];
rb_write_something(data, true);
}
static __init int rb_hammer_test(void *arg)
{
while (!kthread_should_stop()) {
/* Send an IPI to all cpus to write data! */
smp_call_function(rb_ipi, NULL, 1);
/* No sleep, but for non preempt, let others run */
schedule();
}
return 0;
}
static __init int test_ringbuffer(void)
{
struct task_struct *rb_hammer;
struct trace_buffer *buffer;
int cpu;
int ret = 0;
if (security_locked_down(LOCKDOWN_TRACEFS)) {
pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
return 0;
}
pr_info("Running ring buffer tests...\n");
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
if (WARN_ON(!buffer))
return 0;
/* Disable buffer so that threads can't write to it yet */
ring_buffer_record_off(buffer);
for_each_online_cpu(cpu) {
rb_data[cpu].buffer = buffer;
rb_data[cpu].cpu = cpu;
rb_data[cpu].cnt = cpu;
rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
cpu, "rbtester/%u");
if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
pr_cont("FAILED\n");
ret = PTR_ERR(rb_threads[cpu]);
goto out_free;
}
}
/* Now create the rb hammer! */
rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
if (WARN_ON(IS_ERR(rb_hammer))) {
pr_cont("FAILED\n");
ret = PTR_ERR(rb_hammer);
goto out_free;
}
ring_buffer_record_on(buffer);
/*
* Show buffer is enabled before setting rb_test_started.
* Yes there's a small race window where events could be
* dropped and the thread wont catch it. But when a ring
* buffer gets enabled, there will always be some kind of
* delay before other CPUs see it. Thus, we don't care about
* those dropped events. We care about events dropped after
* the threads see that the buffer is active.
*/
smp_wmb();
rb_test_started = true;
set_current_state(TASK_INTERRUPTIBLE);
/* Just run for 10 seconds */;
schedule_timeout(10 * HZ);
kthread_stop(rb_hammer);
out_free:
for_each_online_cpu(cpu) {
if (!rb_threads[cpu])
break;
kthread_stop(rb_threads[cpu]);
}
if (ret) {
ring_buffer_free(buffer);
return ret;
}
/* Report! */
pr_info("finished\n");
for_each_online_cpu(cpu) {
struct ring_buffer_event *event;
struct rb_test_data *data = &rb_data[cpu];
struct rb_item *item;
unsigned long total_events;
unsigned long total_dropped;
unsigned long total_written;
unsigned long total_alloc;
unsigned long total_read = 0;
unsigned long total_size = 0;
unsigned long total_len = 0;
unsigned long total_lost = 0;
unsigned long lost;
int big_event_size;
int small_event_size;
ret = -1;
total_events = data->events + data->events_nested;
total_written = data->bytes_written + data->bytes_written_nested;
total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
big_event_size = data->max_size + data->max_size_nested;
small_event_size = data->min_size + data->min_size_nested;
pr_info("CPU %d:\n", cpu);
pr_info(" events: %ld\n", total_events);
pr_info(" dropped bytes: %ld\n", total_dropped);
pr_info(" alloced bytes: %ld\n", total_alloc);
pr_info(" written bytes: %ld\n", total_written);
pr_info(" biggest event: %d\n", big_event_size);
pr_info(" smallest event: %d\n", small_event_size);
if (RB_WARN_ON(buffer, total_dropped))
break;
ret = 0;
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
total_lost += lost;
item = ring_buffer_event_data(event);
total_len += ring_buffer_event_length(event);
total_size += item->size + sizeof(struct rb_item);
if (memcmp(&item->str[0], rb_string, item->size) != 0) {
pr_info("FAILED!\n");
pr_info("buffer had: %.*s\n", item->size, item->str);
pr_info("expected: %.*s\n", item->size, rb_string);
RB_WARN_ON(buffer, 1);
ret = -1;
break;
}
total_read++;
}
if (ret)
break;
ret = -1;
pr_info(" read events: %ld\n", total_read);
pr_info(" lost events: %ld\n", total_lost);
pr_info(" total events: %ld\n", total_lost + total_read);
pr_info(" recorded len bytes: %ld\n", total_len);
pr_info(" recorded size bytes: %ld\n", total_size);
if (total_lost) {
pr_info(" With dropped events, record len and size may not match\n"
" alloced and written from above\n");
} else {
if (RB_WARN_ON(buffer, total_len != total_alloc ||
total_size != total_written))
break;
}
if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
break;
ret = 0;
}
if (!ret)
pr_info("Ring buffer PASSED!\n");
ring_buffer_free(buffer);
return 0;
}
late_initcall(test_ringbuffer);
#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */