forked from Minki/linux
e4c2ce82ca
The current method of overlaying the page frame as the buffer page pointer can be very dangerous and limits our ability to do other things with a page from the buffer, like send it off to disk. This patch allocates the buffer_page instead of overlaying the page's page frame. The use of the buffer_page has hardly changed due to this. Signed-off-by: Steven Rostedt <srostedt@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
1747 lines
41 KiB
C
1747 lines
41 KiB
C
/*
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* Generic ring buffer
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*
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* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
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*/
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#include <linux/ring_buffer.h>
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#include <linux/spinlock.h>
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#include <linux/debugfs.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/percpu.h>
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#include <linux/mutex.h>
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#include <linux/sched.h> /* used for sched_clock() (for now) */
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/list.h>
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#include <linux/fs.h>
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/* Up this if you want to test the TIME_EXTENTS and normalization */
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#define DEBUG_SHIFT 0
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/* FIXME!!! */
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u64 ring_buffer_time_stamp(int cpu)
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{
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/* shift to debug/test normalization and TIME_EXTENTS */
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return sched_clock() << DEBUG_SHIFT;
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}
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void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
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{
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/* Just stupid testing the normalize function and deltas */
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*ts >>= DEBUG_SHIFT;
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}
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#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
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#define RB_ALIGNMENT_SHIFT 2
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#define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
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#define RB_MAX_SMALL_DATA 28
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enum {
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RB_LEN_TIME_EXTEND = 8,
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RB_LEN_TIME_STAMP = 16,
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};
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/* inline for ring buffer fast paths */
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static inline unsigned
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rb_event_length(struct ring_buffer_event *event)
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{
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unsigned length;
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switch (event->type) {
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case RINGBUF_TYPE_PADDING:
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/* undefined */
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return -1;
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case RINGBUF_TYPE_TIME_EXTEND:
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return RB_LEN_TIME_EXTEND;
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case RINGBUF_TYPE_TIME_STAMP:
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return RB_LEN_TIME_STAMP;
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case RINGBUF_TYPE_DATA:
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if (event->len)
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length = event->len << RB_ALIGNMENT_SHIFT;
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else
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length = event->array[0];
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return length + RB_EVNT_HDR_SIZE;
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default:
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BUG();
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}
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/* not hit */
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return 0;
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}
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/**
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* ring_buffer_event_length - return the length of the event
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* @event: the event to get the length of
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*/
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unsigned ring_buffer_event_length(struct ring_buffer_event *event)
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{
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return rb_event_length(event);
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}
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/* inline for ring buffer fast paths */
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static inline void *
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rb_event_data(struct ring_buffer_event *event)
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{
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BUG_ON(event->type != RINGBUF_TYPE_DATA);
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/* If length is in len field, then array[0] has the data */
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if (event->len)
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return (void *)&event->array[0];
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/* Otherwise length is in array[0] and array[1] has the data */
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return (void *)&event->array[1];
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}
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/**
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* ring_buffer_event_data - return the data of the event
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* @event: the event to get the data from
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*/
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void *ring_buffer_event_data(struct ring_buffer_event *event)
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{
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return rb_event_data(event);
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}
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#define for_each_buffer_cpu(buffer, cpu) \
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for_each_cpu_mask(cpu, buffer->cpumask)
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#define TS_SHIFT 27
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#define TS_MASK ((1ULL << TS_SHIFT) - 1)
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#define TS_DELTA_TEST (~TS_MASK)
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/*
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* This hack stolen from mm/slob.c.
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* We can store per page timing information in the page frame of the page.
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* Thanks to Peter Zijlstra for suggesting this idea.
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*/
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struct buffer_page {
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u64 time_stamp; /* page time stamp */
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unsigned size; /* size of page data */
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struct list_head list; /* list of free pages */
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void *page; /* Actual data page */
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};
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/*
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* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
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* this issue out.
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*/
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static inline void free_buffer_page(struct buffer_page *bpage)
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{
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if (bpage->page)
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__free_page(bpage->page);
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kfree(bpage);
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}
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/*
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* We need to fit the time_stamp delta into 27 bits.
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*/
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static inline int test_time_stamp(u64 delta)
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{
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if (delta & TS_DELTA_TEST)
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return 1;
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return 0;
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}
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#define BUF_PAGE_SIZE PAGE_SIZE
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/*
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* head_page == tail_page && head == tail then buffer is empty.
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*/
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struct ring_buffer_per_cpu {
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int cpu;
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struct ring_buffer *buffer;
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spinlock_t lock;
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struct lock_class_key lock_key;
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struct list_head pages;
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unsigned long head; /* read from head */
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unsigned long tail; /* write to tail */
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unsigned long reader;
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struct buffer_page *head_page;
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struct buffer_page *tail_page;
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struct buffer_page *reader_page;
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unsigned long overrun;
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unsigned long entries;
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u64 write_stamp;
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u64 read_stamp;
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atomic_t record_disabled;
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};
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struct ring_buffer {
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unsigned long size;
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unsigned pages;
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unsigned flags;
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int cpus;
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cpumask_t cpumask;
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atomic_t record_disabled;
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struct mutex mutex;
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struct ring_buffer_per_cpu **buffers;
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};
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struct ring_buffer_iter {
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struct ring_buffer_per_cpu *cpu_buffer;
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unsigned long head;
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struct buffer_page *head_page;
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u64 read_stamp;
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};
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#define RB_WARN_ON(buffer, cond) \
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if (unlikely(cond)) { \
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atomic_inc(&buffer->record_disabled); \
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WARN_ON(1); \
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return -1; \
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}
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/**
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* check_pages - integrity check of buffer pages
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* @cpu_buffer: CPU buffer with pages to test
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*
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* As a safty measure we check to make sure the data pages have not
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* been corrupted.
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*/
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static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
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{
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struct list_head *head = &cpu_buffer->pages;
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struct buffer_page *page, *tmp;
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RB_WARN_ON(cpu_buffer, head->next->prev != head);
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RB_WARN_ON(cpu_buffer, head->prev->next != head);
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list_for_each_entry_safe(page, tmp, head, list) {
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RB_WARN_ON(cpu_buffer, page->list.next->prev != &page->list);
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RB_WARN_ON(cpu_buffer, page->list.prev->next != &page->list);
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}
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return 0;
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}
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static unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
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{
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return cpu_buffer->head_page->size;
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}
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static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
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unsigned nr_pages)
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{
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struct list_head *head = &cpu_buffer->pages;
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struct buffer_page *page, *tmp;
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unsigned long addr;
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LIST_HEAD(pages);
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unsigned i;
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for (i = 0; i < nr_pages; i++) {
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page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
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GFP_KERNEL, cpu_to_node(cpu));
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if (!page)
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goto free_pages;
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list_add(&page->list, &pages);
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addr = __get_free_page(GFP_KERNEL);
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if (!addr)
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goto free_pages;
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page->page = (void *)addr;
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}
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list_splice(&pages, head);
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rb_check_pages(cpu_buffer);
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return 0;
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free_pages:
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list_for_each_entry_safe(page, tmp, &pages, list) {
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list_del_init(&page->list);
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free_buffer_page(page);
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}
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return -ENOMEM;
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}
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static struct ring_buffer_per_cpu *
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rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
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{
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struct ring_buffer_per_cpu *cpu_buffer;
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struct buffer_page *page;
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unsigned long addr;
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int ret;
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cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
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GFP_KERNEL, cpu_to_node(cpu));
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if (!cpu_buffer)
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return NULL;
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cpu_buffer->cpu = cpu;
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cpu_buffer->buffer = buffer;
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spin_lock_init(&cpu_buffer->lock);
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INIT_LIST_HEAD(&cpu_buffer->pages);
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page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
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GFP_KERNEL, cpu_to_node(cpu));
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if (!page)
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goto fail_free_buffer;
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cpu_buffer->reader_page = page;
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addr = __get_free_page(GFP_KERNEL);
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if (!addr)
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goto fail_free_reader;
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page->page = (void *)addr;
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INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
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cpu_buffer->reader_page->size = 0;
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ret = rb_allocate_pages(cpu_buffer, buffer->pages);
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if (ret < 0)
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goto fail_free_reader;
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cpu_buffer->head_page
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= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
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cpu_buffer->tail_page
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= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
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return cpu_buffer;
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fail_free_reader:
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free_buffer_page(cpu_buffer->reader_page);
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fail_free_buffer:
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kfree(cpu_buffer);
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return NULL;
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}
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static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
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{
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struct list_head *head = &cpu_buffer->pages;
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struct buffer_page *page, *tmp;
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list_del_init(&cpu_buffer->reader_page->list);
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free_buffer_page(cpu_buffer->reader_page);
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list_for_each_entry_safe(page, tmp, head, list) {
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list_del_init(&page->list);
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free_buffer_page(page);
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}
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kfree(cpu_buffer);
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}
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/*
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* Causes compile errors if the struct buffer_page gets bigger
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* than the struct page.
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*/
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extern int ring_buffer_page_too_big(void);
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/**
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* ring_buffer_alloc - allocate a new ring_buffer
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* @size: the size in bytes that is needed.
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* @flags: attributes to set for the ring buffer.
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*
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* Currently the only flag that is available is the RB_FL_OVERWRITE
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* flag. This flag means that the buffer will overwrite old data
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* when the buffer wraps. If this flag is not set, the buffer will
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* drop data when the tail hits the head.
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*/
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struct ring_buffer *ring_buffer_alloc(unsigned long size, unsigned flags)
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{
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struct ring_buffer *buffer;
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int bsize;
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int cpu;
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/* Paranoid! Optimizes out when all is well */
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if (sizeof(struct buffer_page) > sizeof(struct page))
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ring_buffer_page_too_big();
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/* keep it in its own cache line */
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buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
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GFP_KERNEL);
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if (!buffer)
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return NULL;
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buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
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buffer->flags = flags;
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/* need at least two pages */
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if (buffer->pages == 1)
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buffer->pages++;
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buffer->cpumask = cpu_possible_map;
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buffer->cpus = nr_cpu_ids;
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bsize = sizeof(void *) * nr_cpu_ids;
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buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
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GFP_KERNEL);
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if (!buffer->buffers)
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goto fail_free_buffer;
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for_each_buffer_cpu(buffer, cpu) {
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buffer->buffers[cpu] =
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rb_allocate_cpu_buffer(buffer, cpu);
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if (!buffer->buffers[cpu])
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goto fail_free_buffers;
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}
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mutex_init(&buffer->mutex);
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return buffer;
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fail_free_buffers:
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for_each_buffer_cpu(buffer, cpu) {
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if (buffer->buffers[cpu])
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rb_free_cpu_buffer(buffer->buffers[cpu]);
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}
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kfree(buffer->buffers);
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fail_free_buffer:
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kfree(buffer);
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return NULL;
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}
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/**
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* ring_buffer_free - free a ring buffer.
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* @buffer: the buffer to free.
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*/
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void
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ring_buffer_free(struct ring_buffer *buffer)
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{
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int cpu;
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for_each_buffer_cpu(buffer, cpu)
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rb_free_cpu_buffer(buffer->buffers[cpu]);
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kfree(buffer);
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}
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static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
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static void
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rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
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{
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struct buffer_page *page;
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struct list_head *p;
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unsigned i;
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atomic_inc(&cpu_buffer->record_disabled);
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synchronize_sched();
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for (i = 0; i < nr_pages; i++) {
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BUG_ON(list_empty(&cpu_buffer->pages));
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p = cpu_buffer->pages.next;
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page = list_entry(p, struct buffer_page, list);
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list_del_init(&page->list);
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free_buffer_page(page);
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}
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BUG_ON(list_empty(&cpu_buffer->pages));
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rb_reset_cpu(cpu_buffer);
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rb_check_pages(cpu_buffer);
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atomic_dec(&cpu_buffer->record_disabled);
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}
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|
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static void
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rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
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struct list_head *pages, unsigned nr_pages)
|
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{
|
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struct buffer_page *page;
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struct list_head *p;
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unsigned i;
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|
|
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atomic_inc(&cpu_buffer->record_disabled);
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synchronize_sched();
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|
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for (i = 0; i < nr_pages; i++) {
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BUG_ON(list_empty(pages));
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p = pages->next;
|
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page = list_entry(p, struct buffer_page, list);
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list_del_init(&page->list);
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list_add_tail(&page->list, &cpu_buffer->pages);
|
|
}
|
|
rb_reset_cpu(cpu_buffer);
|
|
|
|
rb_check_pages(cpu_buffer);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_resize - resize the ring buffer
|
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* @buffer: the buffer to resize.
|
|
* @size: the new size.
|
|
*
|
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* The tracer is responsible for making sure that the buffer is
|
|
* not being used while changing the size.
|
|
* Note: We may be able to change the above requirement by using
|
|
* RCU synchronizations.
|
|
*
|
|
* Minimum size is 2 * BUF_PAGE_SIZE.
|
|
*
|
|
* Returns -1 on failure.
|
|
*/
|
|
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned nr_pages, rm_pages, new_pages;
|
|
struct buffer_page *page, *tmp;
|
|
unsigned long buffer_size;
|
|
unsigned long addr;
|
|
LIST_HEAD(pages);
|
|
int i, cpu;
|
|
|
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size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
size *= BUF_PAGE_SIZE;
|
|
buffer_size = buffer->pages * BUF_PAGE_SIZE;
|
|
|
|
/* we need a minimum of two pages */
|
|
if (size < BUF_PAGE_SIZE * 2)
|
|
size = BUF_PAGE_SIZE * 2;
|
|
|
|
if (size == buffer_size)
|
|
return size;
|
|
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
|
|
|
|
if (size < buffer_size) {
|
|
|
|
/* easy case, just free pages */
|
|
BUG_ON(nr_pages >= buffer->pages);
|
|
|
|
rm_pages = buffer->pages - nr_pages;
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_remove_pages(cpu_buffer, rm_pages);
|
|
}
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* This is a bit more difficult. We only want to add pages
|
|
* when we can allocate enough for all CPUs. We do this
|
|
* by allocating all the pages and storing them on a local
|
|
* link list. If we succeed in our allocation, then we
|
|
* add these pages to the cpu_buffers. Otherwise we just free
|
|
* them all and return -ENOMEM;
|
|
*/
|
|
BUG_ON(nr_pages <= buffer->pages);
|
|
new_pages = nr_pages - buffer->pages;
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
for (i = 0; i < new_pages; i++) {
|
|
page = kzalloc_node(ALIGN(sizeof(*page),
|
|
cache_line_size()),
|
|
GFP_KERNEL, cpu_to_node(cpu));
|
|
if (!page)
|
|
goto free_pages;
|
|
list_add(&page->list, &pages);
|
|
addr = __get_free_page(GFP_KERNEL);
|
|
if (!addr)
|
|
goto free_pages;
|
|
page->page = (void *)addr;
|
|
}
|
|
}
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_insert_pages(cpu_buffer, &pages, new_pages);
|
|
}
|
|
|
|
BUG_ON(!list_empty(&pages));
|
|
|
|
out:
|
|
buffer->pages = nr_pages;
|
|
mutex_unlock(&buffer->mutex);
|
|
|
|
return size;
|
|
|
|
free_pages:
|
|
list_for_each_entry_safe(page, tmp, &pages, list) {
|
|
list_del_init(&page->list);
|
|
free_buffer_page(page);
|
|
}
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return (cpu_buffer->reader == cpu_buffer->reader_page->size &&
|
|
(cpu_buffer->tail_page == cpu_buffer->reader_page ||
|
|
(cpu_buffer->tail_page == cpu_buffer->head_page &&
|
|
cpu_buffer->head == cpu_buffer->tail)));
|
|
}
|
|
|
|
static inline int rb_null_event(struct ring_buffer_event *event)
|
|
{
|
|
return event->type == RINGBUF_TYPE_PADDING;
|
|
}
|
|
|
|
static inline void *rb_page_index(struct buffer_page *page, unsigned index)
|
|
{
|
|
return page->page + index;
|
|
}
|
|
|
|
static 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);
|
|
}
|
|
|
|
static inline struct ring_buffer_event *
|
|
rb_iter_head_event(struct ring_buffer_iter *iter)
|
|
{
|
|
return rb_page_index(iter->head_page,
|
|
iter->head);
|
|
}
|
|
|
|
/*
|
|
* When the tail hits the head and the buffer is in overwrite mode,
|
|
* the head jumps to the next page and all content on the previous
|
|
* page is discarded. But before doing so, we update the overrun
|
|
* variable of the buffer.
|
|
*/
|
|
static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
unsigned long head;
|
|
|
|
for (head = 0; head < rb_head_size(cpu_buffer);
|
|
head += rb_event_length(event)) {
|
|
|
|
event = rb_page_index(cpu_buffer->head_page, head);
|
|
BUG_ON(rb_null_event(event));
|
|
/* Only count data entries */
|
|
if (event->type != RINGBUF_TYPE_DATA)
|
|
continue;
|
|
cpu_buffer->overrun++;
|
|
cpu_buffer->entries--;
|
|
}
|
|
}
|
|
|
|
static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page **page)
|
|
{
|
|
struct list_head *p = (*page)->list.next;
|
|
|
|
if (p == &cpu_buffer->pages)
|
|
p = p->next;
|
|
|
|
*page = list_entry(p, struct buffer_page, list);
|
|
}
|
|
|
|
static inline void
|
|
rb_add_stamp(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts)
|
|
{
|
|
cpu_buffer->tail_page->time_stamp = *ts;
|
|
cpu_buffer->write_stamp = *ts;
|
|
}
|
|
|
|
static void rb_reset_head_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
cpu_buffer->head = 0;
|
|
}
|
|
|
|
static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
|
|
cpu_buffer->reader = 0;
|
|
}
|
|
|
|
static inline 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 = cpu_buffer->head_page;
|
|
else
|
|
rb_inc_page(cpu_buffer, &iter->head_page);
|
|
|
|
iter->read_stamp = iter->head_page->time_stamp;
|
|
iter->head = 0;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_update_event - update event type and data
|
|
* @event: the even to update
|
|
* @type: the type of event
|
|
* @length: the size of the event field in the ring buffer
|
|
*
|
|
* 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 inline void
|
|
rb_update_event(struct ring_buffer_event *event,
|
|
unsigned type, unsigned length)
|
|
{
|
|
event->type = type;
|
|
|
|
switch (type) {
|
|
|
|
case RINGBUF_TYPE_PADDING:
|
|
break;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
event->len =
|
|
(RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
|
|
>> RB_ALIGNMENT_SHIFT;
|
|
break;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
event->len =
|
|
(RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
|
|
>> RB_ALIGNMENT_SHIFT;
|
|
break;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
length -= RB_EVNT_HDR_SIZE;
|
|
if (length > RB_MAX_SMALL_DATA) {
|
|
event->len = 0;
|
|
event->array[0] = length;
|
|
} else
|
|
event->len =
|
|
(length + (RB_ALIGNMENT-1))
|
|
>> RB_ALIGNMENT_SHIFT;
|
|
break;
|
|
default:
|
|
BUG();
|
|
}
|
|
}
|
|
|
|
static inline 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 = 1;
|
|
|
|
if (length > RB_MAX_SMALL_DATA)
|
|
length += sizeof(event.array[0]);
|
|
|
|
length += RB_EVNT_HDR_SIZE;
|
|
length = ALIGN(length, RB_ALIGNMENT);
|
|
|
|
return length;
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned type, unsigned long length, u64 *ts)
|
|
{
|
|
struct buffer_page *tail_page, *head_page, *reader_page;
|
|
unsigned long tail;
|
|
struct ring_buffer *buffer = cpu_buffer->buffer;
|
|
struct ring_buffer_event *event;
|
|
|
|
/* No locking needed for tail page */
|
|
tail_page = cpu_buffer->tail_page;
|
|
tail = cpu_buffer->tail;
|
|
|
|
if (tail + length > BUF_PAGE_SIZE) {
|
|
struct buffer_page *next_page = tail_page;
|
|
|
|
spin_lock(&cpu_buffer->lock);
|
|
rb_inc_page(cpu_buffer, &next_page);
|
|
|
|
head_page = cpu_buffer->head_page;
|
|
reader_page = cpu_buffer->reader_page;
|
|
|
|
/* we grabbed the lock before incrementing */
|
|
WARN_ON(next_page == reader_page);
|
|
|
|
if (next_page == head_page) {
|
|
if (!(buffer->flags & RB_FL_OVERWRITE)) {
|
|
spin_unlock(&cpu_buffer->lock);
|
|
return NULL;
|
|
}
|
|
|
|
/* count overflows */
|
|
rb_update_overflow(cpu_buffer);
|
|
|
|
rb_inc_page(cpu_buffer, &head_page);
|
|
cpu_buffer->head_page = head_page;
|
|
rb_reset_head_page(cpu_buffer);
|
|
}
|
|
|
|
if (tail != BUF_PAGE_SIZE) {
|
|
event = rb_page_index(tail_page, tail);
|
|
/* page padding */
|
|
event->type = RINGBUF_TYPE_PADDING;
|
|
}
|
|
|
|
tail_page->size = tail;
|
|
tail_page = next_page;
|
|
tail_page->size = 0;
|
|
tail = 0;
|
|
cpu_buffer->tail_page = tail_page;
|
|
cpu_buffer->tail = tail;
|
|
rb_add_stamp(cpu_buffer, ts);
|
|
spin_unlock(&cpu_buffer->lock);
|
|
}
|
|
|
|
BUG_ON(tail + length > BUF_PAGE_SIZE);
|
|
|
|
event = rb_page_index(tail_page, tail);
|
|
rb_update_event(event, type, length);
|
|
|
|
return event;
|
|
}
|
|
|
|
static int
|
|
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
u64 *ts, u64 *delta)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
static int once;
|
|
|
|
if (unlikely(*delta > (1ULL << 59) && !once++)) {
|
|
printk(KERN_WARNING "Delta way too big! %llu"
|
|
" ts=%llu write stamp = %llu\n",
|
|
*delta, *ts, cpu_buffer->write_stamp);
|
|
WARN_ON(1);
|
|
}
|
|
|
|
/*
|
|
* The delta is too big, we to add a
|
|
* new timestamp.
|
|
*/
|
|
event = __rb_reserve_next(cpu_buffer,
|
|
RINGBUF_TYPE_TIME_EXTEND,
|
|
RB_LEN_TIME_EXTEND,
|
|
ts);
|
|
if (!event)
|
|
return -1;
|
|
|
|
/* check to see if we went to the next page */
|
|
if (cpu_buffer->tail) {
|
|
/* Still on same page, update timestamp */
|
|
event->time_delta = *delta & TS_MASK;
|
|
event->array[0] = *delta >> TS_SHIFT;
|
|
/* commit the time event */
|
|
cpu_buffer->tail +=
|
|
rb_event_length(event);
|
|
cpu_buffer->write_stamp = *ts;
|
|
*delta = 0;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned type, unsigned long length)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
u64 ts, delta;
|
|
|
|
ts = ring_buffer_time_stamp(cpu_buffer->cpu);
|
|
|
|
if (cpu_buffer->tail) {
|
|
delta = ts - cpu_buffer->write_stamp;
|
|
|
|
if (test_time_stamp(delta)) {
|
|
int ret;
|
|
|
|
ret = rb_add_time_stamp(cpu_buffer, &ts, &delta);
|
|
if (ret < 0)
|
|
return NULL;
|
|
}
|
|
} else {
|
|
spin_lock(&cpu_buffer->lock);
|
|
rb_add_stamp(cpu_buffer, &ts);
|
|
spin_unlock(&cpu_buffer->lock);
|
|
delta = 0;
|
|
}
|
|
|
|
event = __rb_reserve_next(cpu_buffer, type, length, &ts);
|
|
if (!event)
|
|
return NULL;
|
|
|
|
/* If the reserve went to the next page, our delta is zero */
|
|
if (!cpu_buffer->tail)
|
|
delta = 0;
|
|
|
|
event->time_delta = delta;
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
* @flags: a pointer to save the interrupt flags
|
|
*
|
|
* Returns a reseverd 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 ring_buffer *buffer,
|
|
unsigned long length,
|
|
unsigned long *flags)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int cpu;
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
return NULL;
|
|
|
|
local_irq_save(*flags);
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
|
goto out;
|
|
|
|
length = rb_calculate_event_length(length);
|
|
if (length > BUF_PAGE_SIZE)
|
|
return NULL;
|
|
|
|
event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
|
|
if (!event)
|
|
goto out;
|
|
|
|
return event;
|
|
|
|
out:
|
|
local_irq_restore(*flags);
|
|
return NULL;
|
|
}
|
|
|
|
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
cpu_buffer->tail += rb_event_length(event);
|
|
cpu_buffer->tail_page->size = cpu_buffer->tail;
|
|
cpu_buffer->write_stamp += event->time_delta;
|
|
cpu_buffer->entries++;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_unlock_commit - commit a reserved
|
|
* @buffer: The buffer to commit to
|
|
* @event: The event pointer to commit.
|
|
* @flags: the interrupt flags received from ring_buffer_lock_reserve.
|
|
*
|
|
* 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 ring_buffer *buffer,
|
|
struct ring_buffer_event *event,
|
|
unsigned long flags)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu = raw_smp_processor_id();
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
rb_commit(cpu_buffer, event);
|
|
|
|
local_irq_restore(flags);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* 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 ring_buffer *buffer,
|
|
unsigned long length,
|
|
void *data)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned long event_length, flags;
|
|
void *body;
|
|
int ret = -EBUSY;
|
|
int cpu;
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
return -EBUSY;
|
|
|
|
local_irq_save(flags);
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
|
goto out;
|
|
|
|
event_length = rb_calculate_event_length(length);
|
|
event = rb_reserve_next_event(cpu_buffer,
|
|
RINGBUF_TYPE_DATA, event_length);
|
|
if (!event)
|
|
goto out;
|
|
|
|
body = rb_event_data(event);
|
|
|
|
memcpy(body, data, length);
|
|
|
|
rb_commit(cpu_buffer, event);
|
|
|
|
ret = 0;
|
|
out:
|
|
local_irq_restore(flags);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* 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_sched() after this.
|
|
*/
|
|
void ring_buffer_record_disable(struct ring_buffer *buffer)
|
|
{
|
|
atomic_inc(&buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* 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 truely enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable(struct ring_buffer *buffer)
|
|
{
|
|
atomic_dec(&buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* 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_sched() after this.
|
|
*/
|
|
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* 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 truely enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* 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 ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return cpu_buffer->entries;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return cpu_buffer->overrun;
|
|
}
|
|
|
|
/**
|
|
* 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 ring_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 += cpu_buffer->entries;
|
|
}
|
|
|
|
return entries;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_overrun_cpu - 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 ring_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 += cpu_buffer->overrun;
|
|
}
|
|
|
|
return overruns;
|
|
}
|
|
|
|
/**
|
|
* 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 = iter->cpu_buffer;
|
|
|
|
/* Iterator usage is expected to have record disabled */
|
|
if (list_empty(&cpu_buffer->reader_page->list)) {
|
|
iter->head_page = cpu_buffer->head_page;
|
|
iter->head = cpu_buffer->head;
|
|
} else {
|
|
iter->head_page = cpu_buffer->reader_page;
|
|
iter->head = cpu_buffer->reader;
|
|
}
|
|
if (iter->head)
|
|
iter->read_stamp = cpu_buffer->read_stamp;
|
|
else
|
|
iter->read_stamp = iter->head_page->time_stamp;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
return iter->head_page == cpu_buffer->tail_page &&
|
|
iter->head == cpu_buffer->tail;
|
|
}
|
|
|
|
static void
|
|
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = event->array[0];
|
|
delta <<= TS_SHIFT;
|
|
delta += event->time_delta;
|
|
cpu_buffer->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
cpu_buffer->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
return;
|
|
}
|
|
|
|
static void
|
|
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = event->array[0];
|
|
delta <<= TS_SHIFT;
|
|
delta += event->time_delta;
|
|
iter->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
iter->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
return;
|
|
}
|
|
|
|
static struct buffer_page *
|
|
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *reader = NULL;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->lock, flags);
|
|
|
|
again:
|
|
reader = cpu_buffer->reader_page;
|
|
|
|
/* If there's more to read, return this page */
|
|
if (cpu_buffer->reader < reader->size)
|
|
goto out;
|
|
|
|
/* Never should we have an index greater than the size */
|
|
WARN_ON(cpu_buffer->reader > reader->size);
|
|
|
|
/* check if we caught up to the tail */
|
|
reader = NULL;
|
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
|
goto out;
|
|
|
|
/*
|
|
* Splice the empty reader page into the list around the head.
|
|
* Reset the reader page to size zero.
|
|
*/
|
|
|
|
reader = cpu_buffer->head_page;
|
|
cpu_buffer->reader_page->list.next = reader->list.next;
|
|
cpu_buffer->reader_page->list.prev = reader->list.prev;
|
|
cpu_buffer->reader_page->size = 0;
|
|
|
|
/* Make the reader page now replace the head */
|
|
reader->list.prev->next = &cpu_buffer->reader_page->list;
|
|
reader->list.next->prev = &cpu_buffer->reader_page->list;
|
|
|
|
/*
|
|
* If the tail is on the reader, then we must set the head
|
|
* to the inserted page, otherwise we set it one before.
|
|
*/
|
|
cpu_buffer->head_page = cpu_buffer->reader_page;
|
|
|
|
if (cpu_buffer->tail_page != reader)
|
|
rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
|
|
|
|
/* Finally update the reader page to the new head */
|
|
cpu_buffer->reader_page = reader;
|
|
rb_reset_reader_page(cpu_buffer);
|
|
|
|
goto again;
|
|
|
|
out:
|
|
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
|
|
|
|
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 */
|
|
BUG_ON(!reader);
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
if (event->type == RINGBUF_TYPE_DATA)
|
|
cpu_buffer->entries--;
|
|
|
|
rb_update_read_stamp(cpu_buffer, event);
|
|
|
|
length = rb_event_length(event);
|
|
cpu_buffer->reader += length;
|
|
}
|
|
|
|
static void rb_advance_iter(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer *buffer;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned length;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
buffer = cpu_buffer->buffer;
|
|
|
|
/*
|
|
* Check if we are at the end of the buffer.
|
|
*/
|
|
if (iter->head >= iter->head_page->size) {
|
|
BUG_ON(iter->head_page == cpu_buffer->tail_page);
|
|
rb_inc_iter(iter);
|
|
return;
|
|
}
|
|
|
|
event = rb_iter_head_event(iter);
|
|
|
|
length = rb_event_length(event);
|
|
|
|
/*
|
|
* This should not be called to advance the header if we are
|
|
* at the tail of the buffer.
|
|
*/
|
|
BUG_ON((iter->head_page == cpu_buffer->tail_page) &&
|
|
(iter->head + length > cpu_buffer->tail));
|
|
|
|
rb_update_iter_read_stamp(iter, event);
|
|
|
|
iter->head += length;
|
|
|
|
/* check for end of page padding */
|
|
if ((iter->head >= iter->head_page->size) &&
|
|
(iter->head_page != cpu_buffer->tail_page))
|
|
rb_advance_iter(iter);
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* This will return the event that will be read next, but does
|
|
* not consume the data.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *reader;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
again:
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (!reader)
|
|
return NULL;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
switch (event->type) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
WARN_ON(1);
|
|
rb_advance_reader(cpu_buffer);
|
|
return NULL;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts) {
|
|
*ts = cpu_buffer->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
|
|
}
|
|
return event;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* 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 *buffer;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
|
|
if (ring_buffer_iter_empty(iter))
|
|
return NULL;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
buffer = cpu_buffer->buffer;
|
|
|
|
again:
|
|
if (rb_per_cpu_empty(cpu_buffer))
|
|
return NULL;
|
|
|
|
event = rb_iter_head_event(iter);
|
|
|
|
switch (event->type) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
rb_inc_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
/* FIXME: not implemented */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts) {
|
|
*ts = iter->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
|
|
}
|
|
return event;
|
|
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_consume - return an event and consume it
|
|
* @buffer: The ring buffer to get the next event from
|
|
*
|
|
* 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 ring_buffer *buffer, int cpu, u64 *ts)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
event = ring_buffer_peek(buffer, cpu, ts);
|
|
if (!event)
|
|
return NULL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_advance_reader(cpu_buffer);
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_read_start - start a non consuming read of the buffer
|
|
* @buffer: The ring buffer to read from
|
|
* @cpu: The cpu buffer to iterate over
|
|
*
|
|
* This starts up an iteration through the buffer. It also disables
|
|
* the recording to the buffer until the reading is finished.
|
|
* This prevents the reading from being corrupted. This is not
|
|
* a consuming read, so a producer is not expected.
|
|
*
|
|
* Must be paired with ring_buffer_finish.
|
|
*/
|
|
struct ring_buffer_iter *
|
|
ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_iter *iter;
|
|
unsigned long flags;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
|
|
if (!iter)
|
|
return NULL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
iter->cpu_buffer = cpu_buffer;
|
|
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
synchronize_sched();
|
|
|
|
spin_lock_irqsave(&cpu_buffer->lock, flags);
|
|
ring_buffer_iter_reset(iter);
|
|
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
|
|
|
|
return iter;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_finish - finish reading the iterator of the buffer
|
|
* @iter: The iterator retrieved by ring_buffer_start
|
|
*
|
|
* This re-enables the recording to 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;
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
kfree(iter);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_read - read the next item in the ring buffer by the iterator
|
|
* @iter: The ring buffer iterator
|
|
* @ts: The time stamp of the event read.
|
|
*
|
|
* This reads the next event in the ring buffer and increments the iterator.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
|
|
event = ring_buffer_iter_peek(iter, ts);
|
|
if (!event)
|
|
return NULL;
|
|
|
|
rb_advance_iter(iter);
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_size - return the size of the ring buffer (in bytes)
|
|
* @buffer: The ring buffer.
|
|
*/
|
|
unsigned long ring_buffer_size(struct ring_buffer *buffer)
|
|
{
|
|
return BUF_PAGE_SIZE * buffer->pages;
|
|
}
|
|
|
|
static void
|
|
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
|
|
cpu_buffer->head_page->size = 0;
|
|
cpu_buffer->tail_page = cpu_buffer->head_page;
|
|
cpu_buffer->tail_page->size = 0;
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
|
cpu_buffer->reader_page->size = 0;
|
|
|
|
cpu_buffer->head = cpu_buffer->tail = cpu_buffer->reader = 0;
|
|
|
|
cpu_buffer->overrun = 0;
|
|
cpu_buffer->entries = 0;
|
|
}
|
|
|
|
/**
|
|
* 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 ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
unsigned long flags;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->lock, flags);
|
|
|
|
rb_reset_cpu(cpu_buffer);
|
|
|
|
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_reset - reset a ring buffer
|
|
* @buffer: The ring buffer to reset all cpu buffers
|
|
*/
|
|
void ring_buffer_reset(struct ring_buffer *buffer)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_buffer_cpu(buffer, cpu)
|
|
ring_buffer_reset_cpu(buffer, cpu);
|
|
}
|
|
|
|
/**
|
|
* rind_buffer_empty - is the ring buffer empty?
|
|
* @buffer: The ring buffer to test
|
|
*/
|
|
int ring_buffer_empty(struct ring_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
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];
|
|
if (!rb_per_cpu_empty(cpu_buffer))
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
|
|
* @buffer: The ring buffer
|
|
* @cpu: The CPU buffer to test
|
|
*/
|
|
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpu_isset(cpu, buffer->cpumask))
|
|
return 1;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return rb_per_cpu_empty(cpu_buffer);
|
|
}
|
|
|
|
/**
|
|
* 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
|
|
*
|
|
* 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 ring_buffer *buffer_a,
|
|
struct ring_buffer *buffer_b, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer_a;
|
|
struct ring_buffer_per_cpu *cpu_buffer_b;
|
|
|
|
if (!cpu_isset(cpu, buffer_a->cpumask) ||
|
|
!cpu_isset(cpu, buffer_b->cpumask))
|
|
return -EINVAL;
|
|
|
|
/* At least make sure the two buffers are somewhat the same */
|
|
if (buffer_a->size != buffer_b->size ||
|
|
buffer_a->pages != buffer_b->pages)
|
|
return -EINVAL;
|
|
|
|
cpu_buffer_a = buffer_a->buffers[cpu];
|
|
cpu_buffer_b = buffer_b->buffers[cpu];
|
|
|
|
/*
|
|
* We can't do a synchronize_sched 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);
|
|
|
|
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;
|
|
|
|
atomic_dec(&cpu_buffer_a->record_disabled);
|
|
atomic_dec(&cpu_buffer_b->record_disabled);
|
|
|
|
return 0;
|
|
}
|
|
|