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linux/kernel/trace/trace_osnoise.c
Daniel Bristot de Oliveira dd990352f0 tracing/osnoise: Make osnoise_main to sleep for microseconds 
osnoise's runtime and period are in the microseconds scale, but it is
currently sleeping in the millisecond's scale. This behavior roots in the
usage of hwlat as the skeleton for osnoise.

Make osnoise to sleep in the microseconds scale. Also, move the sleep to
a specialized function.

Link: https://lkml.kernel.org/r/302aa6c7bdf2d131719b22901905e9da122a11b2.1645197336.git.bristot@kernel.org

Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2022-02-25 12:07:01 -05:00

2390 lines
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// SPDX-License-Identifier: GPL-2.0
/*
* OS Noise Tracer: computes the OS Noise suffered by a running thread.
* Timerlat Tracer: measures the wakeup latency of a timer triggered IRQ and thread.
*
* Based on "hwlat_detector" tracer by:
* Copyright (C) 2008-2009 Jon Masters, Red Hat, Inc. <jcm@redhat.com>
* Copyright (C) 2013-2016 Steven Rostedt, Red Hat, Inc. <srostedt@redhat.com>
* With feedback from Clark Williams <williams@redhat.com>
*
* And also based on the rtsl tracer presented on:
* DE OLIVEIRA, Daniel Bristot, et al. Demystifying the real-time linux
* scheduling latency. In: 32nd Euromicro Conference on Real-Time Systems
* (ECRTS 2020). Schloss Dagstuhl-Leibniz-Zentrum fur Informatik, 2020.
*
* Copyright (C) 2021 Daniel Bristot de Oliveira, Red Hat, Inc. <bristot@redhat.com>
*/
#include <linux/kthread.h>
#include <linux/tracefs.h>
#include <linux/uaccess.h>
#include <linux/cpumask.h>
#include <linux/delay.h>
#include <linux/sched/clock.h>
#include <uapi/linux/sched/types.h>
#include <linux/sched.h>
#include "trace.h"
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/trace/irq_vectors.h>
#undef TRACE_INCLUDE_PATH
#undef TRACE_INCLUDE_FILE
#endif /* CONFIG_X86_LOCAL_APIC */
#include <trace/events/irq.h>
#include <trace/events/sched.h>
#define CREATE_TRACE_POINTS
#include <trace/events/osnoise.h>
/*
* Default values.
*/
#define BANNER "osnoise: "
#define DEFAULT_SAMPLE_PERIOD 1000000 /* 1s */
#define DEFAULT_SAMPLE_RUNTIME 1000000 /* 1s */
#define DEFAULT_TIMERLAT_PERIOD 1000 /* 1ms */
#define DEFAULT_TIMERLAT_PRIO 95 /* FIFO 95 */
/*
* trace_array of the enabled osnoise/timerlat instances.
*/
struct osnoise_instance {
struct list_head list;
struct trace_array *tr;
};
static struct list_head osnoise_instances;
static bool osnoise_has_registered_instances(void)
{
return !!list_first_or_null_rcu(&osnoise_instances,
struct osnoise_instance,
list);
}
/*
* osnoise_instance_registered - check if a tr is already registered
*/
static int osnoise_instance_registered(struct trace_array *tr)
{
struct osnoise_instance *inst;
int found = 0;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
if (inst->tr == tr)
found = 1;
}
rcu_read_unlock();
return found;
}
/*
* osnoise_register_instance - register a new trace instance
*
* Register a trace_array *tr in the list of instances running
* osnoise/timerlat tracers.
*/
static int osnoise_register_instance(struct trace_array *tr)
{
struct osnoise_instance *inst;
/*
* register/unregister serialization is provided by trace's
* trace_types_lock.
*/
lockdep_assert_held(&trace_types_lock);
inst = kmalloc(sizeof(*inst), GFP_KERNEL);
if (!inst)
return -ENOMEM;
INIT_LIST_HEAD_RCU(&inst->list);
inst->tr = tr;
list_add_tail_rcu(&inst->list, &osnoise_instances);
return 0;
}
/*
* osnoise_unregister_instance - unregister a registered trace instance
*
* Remove the trace_array *tr from the list of instances running
* osnoise/timerlat tracers.
*/
static void osnoise_unregister_instance(struct trace_array *tr)
{
struct osnoise_instance *inst;
int found = 0;
/*
* register/unregister serialization is provided by trace's
* trace_types_lock.
*/
lockdep_assert_held(&trace_types_lock);
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
if (inst->tr == tr) {
list_del_rcu(&inst->list);
found = 1;
break;
}
}
if (!found)
return;
kvfree_rcu(inst);
}
/*
* NMI runtime info.
*/
struct osn_nmi {
u64 count;
u64 delta_start;
};
/*
* IRQ runtime info.
*/
struct osn_irq {
u64 count;
u64 arrival_time;
u64 delta_start;
};
#define IRQ_CONTEXT 0
#define THREAD_CONTEXT 1
/*
* sofirq runtime info.
*/
struct osn_softirq {
u64 count;
u64 arrival_time;
u64 delta_start;
};
/*
* thread runtime info.
*/
struct osn_thread {
u64 count;
u64 arrival_time;
u64 delta_start;
};
/*
* Runtime information: this structure saves the runtime information used by
* one sampling thread.
*/
struct osnoise_variables {
struct task_struct *kthread;
bool sampling;
pid_t pid;
struct osn_nmi nmi;
struct osn_irq irq;
struct osn_softirq softirq;
struct osn_thread thread;
local_t int_counter;
};
/*
* Per-cpu runtime information.
*/
DEFINE_PER_CPU(struct osnoise_variables, per_cpu_osnoise_var);
/*
* this_cpu_osn_var - Return the per-cpu osnoise_variables on its relative CPU
*/
static inline struct osnoise_variables *this_cpu_osn_var(void)
{
return this_cpu_ptr(&per_cpu_osnoise_var);
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* Runtime information for the timer mode.
*/
struct timerlat_variables {
struct task_struct *kthread;
struct hrtimer timer;
u64 rel_period;
u64 abs_period;
bool tracing_thread;
u64 count;
};
DEFINE_PER_CPU(struct timerlat_variables, per_cpu_timerlat_var);
/*
* this_cpu_tmr_var - Return the per-cpu timerlat_variables on its relative CPU
*/
static inline struct timerlat_variables *this_cpu_tmr_var(void)
{
return this_cpu_ptr(&per_cpu_timerlat_var);
}
/*
* tlat_var_reset - Reset the values of the given timerlat_variables
*/
static inline void tlat_var_reset(void)
{
struct timerlat_variables *tlat_var;
int cpu;
/*
* So far, all the values are initialized as 0, so
* zeroing the structure is perfect.
*/
for_each_cpu(cpu, cpu_online_mask) {
tlat_var = per_cpu_ptr(&per_cpu_timerlat_var, cpu);
memset(tlat_var, 0, sizeof(*tlat_var));
}
}
#else /* CONFIG_TIMERLAT_TRACER */
#define tlat_var_reset() do {} while (0)
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* osn_var_reset - Reset the values of the given osnoise_variables
*/
static inline void osn_var_reset(void)
{
struct osnoise_variables *osn_var;
int cpu;
/*
* So far, all the values are initialized as 0, so
* zeroing the structure is perfect.
*/
for_each_cpu(cpu, cpu_online_mask) {
osn_var = per_cpu_ptr(&per_cpu_osnoise_var, cpu);
memset(osn_var, 0, sizeof(*osn_var));
}
}
/*
* osn_var_reset_all - Reset the value of all per-cpu osnoise_variables
*/
static inline void osn_var_reset_all(void)
{
osn_var_reset();
tlat_var_reset();
}
/*
* Tells NMIs to call back to the osnoise tracer to record timestamps.
*/
bool trace_osnoise_callback_enabled;
/*
* osnoise sample structure definition. Used to store the statistics of a
* sample run.
*/
struct osnoise_sample {
u64 runtime; /* runtime */
u64 noise; /* noise */
u64 max_sample; /* max single noise sample */
int hw_count; /* # HW (incl. hypervisor) interference */
int nmi_count; /* # NMIs during this sample */
int irq_count; /* # IRQs during this sample */
int softirq_count; /* # softirqs during this sample */
int thread_count; /* # threads during this sample */
};
#ifdef CONFIG_TIMERLAT_TRACER
/*
* timerlat sample structure definition. Used to store the statistics of
* a sample run.
*/
struct timerlat_sample {
u64 timer_latency; /* timer_latency */
unsigned int seqnum; /* unique sequence */
int context; /* timer context */
};
#endif
/*
* Protect the interface.
*/
struct mutex interface_lock;
/*
* Tracer data.
*/
static struct osnoise_data {
u64 sample_period; /* total sampling period */
u64 sample_runtime; /* active sampling portion of period */
u64 stop_tracing; /* stop trace in the internal operation (loop/irq) */
u64 stop_tracing_total; /* stop trace in the final operation (report/thread) */
#ifdef CONFIG_TIMERLAT_TRACER
u64 timerlat_period; /* timerlat period */
u64 print_stack; /* print IRQ stack if total > */
int timerlat_tracer; /* timerlat tracer */
#endif
bool tainted; /* infor users and developers about a problem */
} osnoise_data = {
.sample_period = DEFAULT_SAMPLE_PERIOD,
.sample_runtime = DEFAULT_SAMPLE_RUNTIME,
.stop_tracing = 0,
.stop_tracing_total = 0,
#ifdef CONFIG_TIMERLAT_TRACER
.print_stack = 0,
.timerlat_period = DEFAULT_TIMERLAT_PERIOD,
.timerlat_tracer = 0,
#endif
};
#ifdef CONFIG_TIMERLAT_TRACER
static inline bool timerlat_enabled(void)
{
return osnoise_data.timerlat_tracer;
}
static inline int timerlat_softirq_exit(struct osnoise_variables *osn_var)
{
struct timerlat_variables *tlat_var = this_cpu_tmr_var();
/*
* If the timerlat is enabled, but the irq handler did
* not run yet enabling timerlat_tracer, do not trace.
*/
if (!tlat_var->tracing_thread) {
osn_var->softirq.arrival_time = 0;
osn_var->softirq.delta_start = 0;
return 0;
}
return 1;
}
static inline int timerlat_thread_exit(struct osnoise_variables *osn_var)
{
struct timerlat_variables *tlat_var = this_cpu_tmr_var();
/*
* If the timerlat is enabled, but the irq handler did
* not run yet enabling timerlat_tracer, do not trace.
*/
if (!tlat_var->tracing_thread) {
osn_var->thread.delta_start = 0;
osn_var->thread.arrival_time = 0;
return 0;
}
return 1;
}
#else /* CONFIG_TIMERLAT_TRACER */
static inline bool timerlat_enabled(void)
{
return false;
}
static inline int timerlat_softirq_exit(struct osnoise_variables *osn_var)
{
return 1;
}
static inline int timerlat_thread_exit(struct osnoise_variables *osn_var)
{
return 1;
}
#endif
#ifdef CONFIG_PREEMPT_RT
/*
* Print the osnoise header info.
*/
static void print_osnoise_headers(struct seq_file *s)
{
if (osnoise_data.tainted)
seq_puts(s, "# osnoise is tainted!\n");
seq_puts(s, "# _-------=> irqs-off\n");
seq_puts(s, "# / _------=> need-resched\n");
seq_puts(s, "# | / _-----=> need-resched-lazy\n");
seq_puts(s, "# || / _----=> hardirq/softirq\n");
seq_puts(s, "# ||| / _---=> preempt-depth\n");
seq_puts(s, "# |||| / _--=> preempt-lazy-depth\n");
seq_puts(s, "# ||||| / _-=> migrate-disable\n");
seq_puts(s, "# |||||| / ");
seq_puts(s, " MAX\n");
seq_puts(s, "# ||||| / ");
seq_puts(s, " SINGLE Interference counters:\n");
seq_puts(s, "# ||||||| RUNTIME ");
seq_puts(s, " NOISE %% OF CPU NOISE +-----------------------------+\n");
seq_puts(s, "# TASK-PID CPU# ||||||| TIMESTAMP IN US ");
seq_puts(s, " IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD\n");
seq_puts(s, "# | | | ||||||| | | ");
seq_puts(s, " | | | | | | | |\n");
}
#else /* CONFIG_PREEMPT_RT */
static void print_osnoise_headers(struct seq_file *s)
{
if (osnoise_data.tainted)
seq_puts(s, "# osnoise is tainted!\n");
seq_puts(s, "# _-----=> irqs-off\n");
seq_puts(s, "# / _----=> need-resched\n");
seq_puts(s, "# | / _---=> hardirq/softirq\n");
seq_puts(s, "# || / _--=> preempt-depth\n");
seq_puts(s, "# ||| / _-=> migrate-disable ");
seq_puts(s, " MAX\n");
seq_puts(s, "# |||| / delay ");
seq_puts(s, " SINGLE Interference counters:\n");
seq_puts(s, "# ||||| RUNTIME ");
seq_puts(s, " NOISE %% OF CPU NOISE +-----------------------------+\n");
seq_puts(s, "# TASK-PID CPU# ||||| TIMESTAMP IN US ");
seq_puts(s, " IN US AVAILABLE IN US HW NMI IRQ SIRQ THREAD\n");
seq_puts(s, "# | | | ||||| | | ");
seq_puts(s, " | | | | | | | |\n");
}
#endif /* CONFIG_PREEMPT_RT */
/*
* osnoise_taint - report an osnoise error.
*/
#define osnoise_taint(msg) ({ \
struct osnoise_instance *inst; \
struct trace_buffer *buffer; \
\
rcu_read_lock(); \
list_for_each_entry_rcu(inst, &osnoise_instances, list) { \
buffer = inst->tr->array_buffer.buffer; \
trace_array_printk_buf(buffer, _THIS_IP_, msg); \
} \
rcu_read_unlock(); \
osnoise_data.tainted = true; \
})
/*
* Record an osnoise_sample into the tracer buffer.
*/
static void
__trace_osnoise_sample(struct osnoise_sample *sample, struct trace_buffer *buffer)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct osnoise_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_OSNOISE, sizeof(*entry),
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
entry->runtime = sample->runtime;
entry->noise = sample->noise;
entry->max_sample = sample->max_sample;
entry->hw_count = sample->hw_count;
entry->nmi_count = sample->nmi_count;
entry->irq_count = sample->irq_count;
entry->softirq_count = sample->softirq_count;
entry->thread_count = sample->thread_count;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* Record an osnoise_sample on all osnoise instances.
*/
static void trace_osnoise_sample(struct osnoise_sample *sample)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__trace_osnoise_sample(sample, buffer);
}
rcu_read_unlock();
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* Print the timerlat header info.
*/
#ifdef CONFIG_PREEMPT_RT
static void print_timerlat_headers(struct seq_file *s)
{
seq_puts(s, "# _-------=> irqs-off\n");
seq_puts(s, "# / _------=> need-resched\n");
seq_puts(s, "# | / _-----=> need-resched-lazy\n");
seq_puts(s, "# || / _----=> hardirq/softirq\n");
seq_puts(s, "# ||| / _---=> preempt-depth\n");
seq_puts(s, "# |||| / _--=> preempt-lazy-depth\n");
seq_puts(s, "# ||||| / _-=> migrate-disable\n");
seq_puts(s, "# |||||| /\n");
seq_puts(s, "# ||||||| ACTIVATION\n");
seq_puts(s, "# TASK-PID CPU# ||||||| TIMESTAMP ID ");
seq_puts(s, " CONTEXT LATENCY\n");
seq_puts(s, "# | | | ||||||| | | ");
seq_puts(s, " | |\n");
}
#else /* CONFIG_PREEMPT_RT */
static void print_timerlat_headers(struct seq_file *s)
{
seq_puts(s, "# _-----=> irqs-off\n");
seq_puts(s, "# / _----=> need-resched\n");
seq_puts(s, "# | / _---=> hardirq/softirq\n");
seq_puts(s, "# || / _--=> preempt-depth\n");
seq_puts(s, "# ||| / _-=> migrate-disable\n");
seq_puts(s, "# |||| / delay\n");
seq_puts(s, "# ||||| ACTIVATION\n");
seq_puts(s, "# TASK-PID CPU# ||||| TIMESTAMP ID ");
seq_puts(s, " CONTEXT LATENCY\n");
seq_puts(s, "# | | | ||||| | | ");
seq_puts(s, " | |\n");
}
#endif /* CONFIG_PREEMPT_RT */
static void
__trace_timerlat_sample(struct timerlat_sample *sample, struct trace_buffer *buffer)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct timerlat_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_TIMERLAT, sizeof(*entry),
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
entry->seqnum = sample->seqnum;
entry->context = sample->context;
entry->timer_latency = sample->timer_latency;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* Record an timerlat_sample into the tracer buffer.
*/
static void trace_timerlat_sample(struct timerlat_sample *sample)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__trace_timerlat_sample(sample, buffer);
}
rcu_read_unlock();
}
#ifdef CONFIG_STACKTRACE
#define MAX_CALLS 256
/*
* Stack trace will take place only at IRQ level, so, no need
* to control nesting here.
*/
struct trace_stack {
int stack_size;
int nr_entries;
unsigned long calls[MAX_CALLS];
};
static DEFINE_PER_CPU(struct trace_stack, trace_stack);
/*
* timerlat_save_stack - save a stack trace without printing
*
* Save the current stack trace without printing. The
* stack will be printed later, after the end of the measurement.
*/
static void timerlat_save_stack(int skip)
{
unsigned int size, nr_entries;
struct trace_stack *fstack;
fstack = this_cpu_ptr(&trace_stack);
size = ARRAY_SIZE(fstack->calls);
nr_entries = stack_trace_save(fstack->calls, size, skip);
fstack->stack_size = nr_entries * sizeof(unsigned long);
fstack->nr_entries = nr_entries;
return;
}
static void
__timerlat_dump_stack(struct trace_buffer *buffer, struct trace_stack *fstack, unsigned int size)
{
struct trace_event_call *call = &event_osnoise;
struct ring_buffer_event *event;
struct stack_entry *entry;
event = trace_buffer_lock_reserve(buffer, TRACE_STACK, sizeof(*entry) + size,
tracing_gen_ctx());
if (!event)
return;
entry = ring_buffer_event_data(event);
memcpy(&entry->caller, fstack->calls, size);
entry->size = fstack->nr_entries;
if (!call_filter_check_discard(call, entry, buffer, event))
trace_buffer_unlock_commit_nostack(buffer, event);
}
/*
* timerlat_dump_stack - dump a stack trace previously saved
*/
static void timerlat_dump_stack(u64 latency)
{
struct osnoise_instance *inst;
struct trace_buffer *buffer;
struct trace_stack *fstack;
unsigned int size;
/*
* trace only if latency > print_stack config, if enabled.
*/
if (!osnoise_data.print_stack || osnoise_data.print_stack > latency)
return;
preempt_disable_notrace();
fstack = this_cpu_ptr(&trace_stack);
size = fstack->stack_size;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
buffer = inst->tr->array_buffer.buffer;
__timerlat_dump_stack(buffer, fstack, size);
}
rcu_read_unlock();
preempt_enable_notrace();
}
#else /* CONFIG_STACKTRACE */
#define timerlat_dump_stack(u64 latency) do {} while (0)
#define timerlat_save_stack(a) do {} while (0)
#endif /* CONFIG_STACKTRACE */
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* Macros to encapsulate the time capturing infrastructure.
*/
#define time_get() trace_clock_local()
#define time_to_us(x) div_u64(x, 1000)
#define time_sub(a, b) ((a) - (b))
/*
* cond_move_irq_delta_start - Forward the delta_start of a running IRQ
*
* If an IRQ is preempted by an NMI, its delta_start is pushed forward
* to discount the NMI interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_irq_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->irq.delta_start)
osn_var->irq.delta_start += duration;
}
#ifndef CONFIG_PREEMPT_RT
/*
* cond_move_softirq_delta_start - Forward the delta_start of a running softirq.
*
* If a softirq is preempted by an IRQ or NMI, its delta_start is pushed
* forward to discount the interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_softirq_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->softirq.delta_start)
osn_var->softirq.delta_start += duration;
}
#else /* CONFIG_PREEMPT_RT */
#define cond_move_softirq_delta_start(osn_var, duration) do {} while (0)
#endif
/*
* cond_move_thread_delta_start - Forward the delta_start of a running thread
*
* If a noisy thread is preempted by an softirq, IRQ or NMI, its delta_start
* is pushed forward to discount the interference.
*
* See get_int_safe_duration().
*/
static inline void
cond_move_thread_delta_start(struct osnoise_variables *osn_var, u64 duration)
{
if (osn_var->thread.delta_start)
osn_var->thread.delta_start += duration;
}
/*
* get_int_safe_duration - Get the duration of a window
*
* The irq, softirq and thread varaibles need to have its duration without
* the interference from higher priority interrupts. Instead of keeping a
* variable to discount the interrupt interference from these variables, the
* starting time of these variables are pushed forward with the interrupt's
* duration. In this way, a single variable is used to:
*
* - Know if a given window is being measured.
* - Account its duration.
* - Discount the interference.
*
* To avoid getting inconsistent values, e.g.,:
*
* now = time_get()
* ---> interrupt!
* delta_start -= int duration;
* <---
* duration = now - delta_start;
*
* result: negative duration if the variable duration before the
* interrupt was smaller than the interrupt execution.
*
* A counter of interrupts is used. If the counter increased, try
* to capture an interference safe duration.
*/
static inline s64
get_int_safe_duration(struct osnoise_variables *osn_var, u64 *delta_start)
{
u64 int_counter, now;
s64 duration;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
now = time_get();
duration = (now - *delta_start);
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
/*
* This is an evidence of race conditions that cause
* a value to be "discounted" too much.
*/
if (duration < 0)
osnoise_taint("Negative duration!\n");
*delta_start = 0;
return duration;
}
/*
*
* set_int_safe_time - Save the current time on *time, aware of interference
*
* Get the time, taking into consideration a possible interference from
* higher priority interrupts.
*
* See get_int_safe_duration() for an explanation.
*/
static u64
set_int_safe_time(struct osnoise_variables *osn_var, u64 *time)
{
u64 int_counter;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
*time = time_get();
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
return int_counter;
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* copy_int_safe_time - Copy *src into *desc aware of interference
*/
static u64
copy_int_safe_time(struct osnoise_variables *osn_var, u64 *dst, u64 *src)
{
u64 int_counter;
do {
int_counter = local_read(&osn_var->int_counter);
/* synchronize with interrupts */
barrier();
*dst = *src;
/* synchronize with interrupts */
barrier();
} while (int_counter != local_read(&osn_var->int_counter));
return int_counter;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* trace_osnoise_callback - NMI entry/exit callback
*
* This function is called at the entry and exit NMI code. The bool enter
* distinguishes between either case. This function is used to note a NMI
* occurrence, compute the noise caused by the NMI, and to remove the noise
* it is potentially causing on other interference variables.
*/
void trace_osnoise_callback(bool enter)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
u64 duration;
if (!osn_var->sampling)
return;
/*
* Currently trace_clock_local() calls sched_clock() and the
* generic version is not NMI safe.
*/
if (!IS_ENABLED(CONFIG_GENERIC_SCHED_CLOCK)) {
if (enter) {
osn_var->nmi.delta_start = time_get();
local_inc(&osn_var->int_counter);
} else {
duration = time_get() - osn_var->nmi.delta_start;
trace_nmi_noise(osn_var->nmi.delta_start, duration);
cond_move_irq_delta_start(osn_var, duration);
cond_move_softirq_delta_start(osn_var, duration);
cond_move_thread_delta_start(osn_var, duration);
}
}
if (enter)
osn_var->nmi.count++;
}
/*
* osnoise_trace_irq_entry - Note the starting of an IRQ
*
* Save the starting time of an IRQ. As IRQs are non-preemptive to other IRQs,
* it is safe to use a single variable (ons_var->irq) to save the statistics.
* The arrival_time is used to report... the arrival time. The delta_start
* is used to compute the duration at the IRQ exit handler. See
* cond_move_irq_delta_start().
*/
void osnoise_trace_irq_entry(int id)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (!osn_var->sampling)
return;
/*
* This value will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->irq.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->irq.delta_start);
osn_var->irq.count++;
local_inc(&osn_var->int_counter);
}
/*
* osnoise_irq_exit - Note the end of an IRQ, sava data and trace
*
* Computes the duration of the IRQ noise, and trace it. Also discounts the
* interference from other sources of noise could be currently being accounted.
*/
void osnoise_trace_irq_exit(int id, const char *desc)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
int duration;
if (!osn_var->sampling)
return;
duration = get_int_safe_duration(osn_var, &osn_var->irq.delta_start);
trace_irq_noise(id, desc, osn_var->irq.arrival_time, duration);
osn_var->irq.arrival_time = 0;
cond_move_softirq_delta_start(osn_var, duration);
cond_move_thread_delta_start(osn_var, duration);
}
/*
* trace_irqentry_callback - Callback to the irq:irq_entry traceevent
*
* Used to note the starting of an IRQ occurece.
*/
static void trace_irqentry_callback(void *data, int irq,
struct irqaction *action)
{
osnoise_trace_irq_entry(irq);
}
/*
* trace_irqexit_callback - Callback to the irq:irq_exit traceevent
*
* Used to note the end of an IRQ occurece.
*/
static void trace_irqexit_callback(void *data, int irq,
struct irqaction *action, int ret)
{
osnoise_trace_irq_exit(irq, action->name);
}
/*
* arch specific register function.
*/
int __weak osnoise_arch_register(void)
{
return 0;
}
/*
* arch specific unregister function.
*/
void __weak osnoise_arch_unregister(void)
{
return;
}
/*
* hook_irq_events - Hook IRQ handling events
*
* This function hooks the IRQ related callbacks to the respective trace
* events.
*/
static int hook_irq_events(void)
{
int ret;
ret = register_trace_irq_handler_entry(trace_irqentry_callback, NULL);
if (ret)
goto out_err;
ret = register_trace_irq_handler_exit(trace_irqexit_callback, NULL);
if (ret)
goto out_unregister_entry;
ret = osnoise_arch_register();
if (ret)
goto out_irq_exit;
return 0;
out_irq_exit:
unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL);
out_unregister_entry:
unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL);
out_err:
return -EINVAL;
}
/*
* unhook_irq_events - Unhook IRQ handling events
*
* This function unhooks the IRQ related callbacks to the respective trace
* events.
*/
static void unhook_irq_events(void)
{
osnoise_arch_unregister();
unregister_trace_irq_handler_exit(trace_irqexit_callback, NULL);
unregister_trace_irq_handler_entry(trace_irqentry_callback, NULL);
}
#ifndef CONFIG_PREEMPT_RT
/*
* trace_softirq_entry_callback - Note the starting of a softirq
*
* Save the starting time of a softirq. As softirqs are non-preemptive to
* other softirqs, it is safe to use a single variable (ons_var->softirq)
* to save the statistics. The arrival_time is used to report... the
* arrival time. The delta_start is used to compute the duration at the
* softirq exit handler. See cond_move_softirq_delta_start().
*/
static void trace_softirq_entry_callback(void *data, unsigned int vec_nr)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (!osn_var->sampling)
return;
/*
* This value will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->softirq.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->softirq.delta_start);
osn_var->softirq.count++;
local_inc(&osn_var->int_counter);
}
/*
* trace_softirq_exit_callback - Note the end of an softirq
*
* Computes the duration of the softirq noise, and trace it. Also discounts the
* interference from other sources of noise could be currently being accounted.
*/
static void trace_softirq_exit_callback(void *data, unsigned int vec_nr)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
int duration;
if (!osn_var->sampling)
return;
if (unlikely(timerlat_enabled()))
if (!timerlat_softirq_exit(osn_var))
return;
duration = get_int_safe_duration(osn_var, &osn_var->softirq.delta_start);
trace_softirq_noise(vec_nr, osn_var->softirq.arrival_time, duration);
cond_move_thread_delta_start(osn_var, duration);
osn_var->softirq.arrival_time = 0;
}
/*
* hook_softirq_events - Hook softirq handling events
*
* This function hooks the softirq related callbacks to the respective trace
* events.
*/
static int hook_softirq_events(void)
{
int ret;
ret = register_trace_softirq_entry(trace_softirq_entry_callback, NULL);
if (ret)
goto out_err;
ret = register_trace_softirq_exit(trace_softirq_exit_callback, NULL);
if (ret)
goto out_unreg_entry;
return 0;
out_unreg_entry:
unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL);
out_err:
return -EINVAL;
}
/*
* unhook_softirq_events - Unhook softirq handling events
*
* This function hooks the softirq related callbacks to the respective trace
* events.
*/
static void unhook_softirq_events(void)
{
unregister_trace_softirq_entry(trace_softirq_entry_callback, NULL);
unregister_trace_softirq_exit(trace_softirq_exit_callback, NULL);
}
#else /* CONFIG_PREEMPT_RT */
/*
* softirq are threads on the PREEMPT_RT mode.
*/
static int hook_softirq_events(void)
{
return 0;
}
static void unhook_softirq_events(void)
{
}
#endif
/*
* thread_entry - Record the starting of a thread noise window
*
* It saves the context switch time for a noisy thread, and increments
* the interference counters.
*/
static void
thread_entry(struct osnoise_variables *osn_var, struct task_struct *t)
{
if (!osn_var->sampling)
return;
/*
* The arrival time will be used in the report, but not to compute
* the execution time, so it is safe to get it unsafe.
*/
osn_var->thread.arrival_time = time_get();
set_int_safe_time(osn_var, &osn_var->thread.delta_start);
osn_var->thread.count++;
local_inc(&osn_var->int_counter);
}
/*
* thread_exit - Report the end of a thread noise window
*
* It computes the total noise from a thread, tracing if needed.
*/
static void
thread_exit(struct osnoise_variables *osn_var, struct task_struct *t)
{
int duration;
if (!osn_var->sampling)
return;
if (unlikely(timerlat_enabled()))
if (!timerlat_thread_exit(osn_var))
return;
duration = get_int_safe_duration(osn_var, &osn_var->thread.delta_start);
trace_thread_noise(t, osn_var->thread.arrival_time, duration);
osn_var->thread.arrival_time = 0;
}
/*
* trace_sched_switch - sched:sched_switch trace event handler
*
* This function is hooked to the sched:sched_switch trace event, and it is
* used to record the beginning and to report the end of a thread noise window.
*/
static void
trace_sched_switch_callback(void *data, bool preempt, struct task_struct *p,
struct task_struct *n)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
if (p->pid != osn_var->pid)
thread_exit(osn_var, p);
if (n->pid != osn_var->pid)
thread_entry(osn_var, n);
}
/*
* hook_thread_events - Hook the insturmentation for thread noise
*
* Hook the osnoise tracer callbacks to handle the noise from other
* threads on the necessary kernel events.
*/
static int hook_thread_events(void)
{
int ret;
ret = register_trace_sched_switch(trace_sched_switch_callback, NULL);
if (ret)
return -EINVAL;
return 0;
}
/*
* unhook_thread_events - *nhook the insturmentation for thread noise
*
* Unook the osnoise tracer callbacks to handle the noise from other
* threads on the necessary kernel events.
*/
static void unhook_thread_events(void)
{
unregister_trace_sched_switch(trace_sched_switch_callback, NULL);
}
/*
* save_osn_sample_stats - Save the osnoise_sample statistics
*
* Save the osnoise_sample statistics before the sampling phase. These
* values will be used later to compute the diff betwneen the statistics
* before and after the osnoise sampling.
*/
static void
save_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s)
{
s->nmi_count = osn_var->nmi.count;
s->irq_count = osn_var->irq.count;
s->softirq_count = osn_var->softirq.count;
s->thread_count = osn_var->thread.count;
}
/*
* diff_osn_sample_stats - Compute the osnoise_sample statistics
*
* After a sample period, compute the difference on the osnoise_sample
* statistics. The struct osnoise_sample *s contains the statistics saved via
* save_osn_sample_stats() before the osnoise sampling.
*/
static void
diff_osn_sample_stats(struct osnoise_variables *osn_var, struct osnoise_sample *s)
{
s->nmi_count = osn_var->nmi.count - s->nmi_count;
s->irq_count = osn_var->irq.count - s->irq_count;
s->softirq_count = osn_var->softirq.count - s->softirq_count;
s->thread_count = osn_var->thread.count - s->thread_count;
}
/*
* osnoise_stop_tracing - Stop tracing and the tracer.
*/
static __always_inline void osnoise_stop_tracing(void)
{
struct osnoise_instance *inst;
struct trace_array *tr;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
tr = inst->tr;
trace_array_printk_buf(tr->array_buffer.buffer, _THIS_IP_,
"stop tracing hit on cpu %d\n", smp_processor_id());
tracer_tracing_off(tr);
}
rcu_read_unlock();
}
/*
* notify_new_max_latency - Notify a new max latency via fsnotify interface.
*/
static void notify_new_max_latency(u64 latency)
{
struct osnoise_instance *inst;
struct trace_array *tr;
rcu_read_lock();
list_for_each_entry_rcu(inst, &osnoise_instances, list) {
tr = inst->tr;
if (tr->max_latency < latency) {
tr->max_latency = latency;
latency_fsnotify(tr);
}
}
rcu_read_unlock();
}
/*
* run_osnoise - Sample the time and look for osnoise
*
* Used to capture the time, looking for potential osnoise latency repeatedly.
* Different from hwlat_detector, it is called with preemption and interrupts
* enabled. This allows irqs, softirqs and threads to run, interfering on the
* osnoise sampling thread, as they would do with a regular thread.
*/
static int run_osnoise(void)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
u64 start, sample, last_sample;
u64 last_int_count, int_count;
s64 noise = 0, max_noise = 0;
s64 total, last_total = 0;
struct osnoise_sample s;
unsigned int threshold;
u64 runtime, stop_in;
u64 sum_noise = 0;
int hw_count = 0;
int ret = -1;
/*
* Considers the current thread as the workload.
*/
osn_var->pid = current->pid;
/*
* Save the current stats for the diff
*/
save_osn_sample_stats(osn_var, &s);
/*
* if threshold is 0, use the default value of 5 us.
*/
threshold = tracing_thresh ? : 5000;
/*
* Make sure NMIs see sampling first
*/
osn_var->sampling = true;
barrier();
/*
* Transform the *_us config to nanoseconds to avoid the
* division on the main loop.
*/
runtime = osnoise_data.sample_runtime * NSEC_PER_USEC;
stop_in = osnoise_data.stop_tracing * NSEC_PER_USEC;
/*
* Start timestemp
*/
start = time_get();
/*
* "previous" loop.
*/
last_int_count = set_int_safe_time(osn_var, &last_sample);
do {
/*
* Get sample!
*/
int_count = set_int_safe_time(osn_var, &sample);
noise = time_sub(sample, last_sample);
/*
* This shouldn't happen.
*/
if (noise < 0) {
osnoise_taint("negative noise!");
goto out;
}
/*
* Sample runtime.
*/
total = time_sub(sample, start);
/*
* Check for possible overflows.
*/
if (total < last_total) {
osnoise_taint("total overflow!");
break;
}
last_total = total;
if (noise >= threshold) {
int interference = int_count - last_int_count;
if (noise > max_noise)
max_noise = noise;
if (!interference)
hw_count++;
sum_noise += noise;
trace_sample_threshold(last_sample, noise, interference);
if (osnoise_data.stop_tracing)
if (noise > stop_in)
osnoise_stop_tracing();
}
/*
* For the non-preemptive kernel config: let threads runs, if
* they so wish.
*/
cond_resched();
last_sample = sample;
last_int_count = int_count;
} while (total < runtime && !kthread_should_stop());
/*
* Finish the above in the view for interrupts.
*/
barrier();
osn_var->sampling = false;
/*
* Make sure sampling data is no longer updated.
*/
barrier();
/*
* Save noise info.
*/
s.noise = time_to_us(sum_noise);
s.runtime = time_to_us(total);
s.max_sample = time_to_us(max_noise);
s.hw_count = hw_count;
/* Save interference stats info */
diff_osn_sample_stats(osn_var, &s);
trace_osnoise_sample(&s);
notify_new_max_latency(max_noise);
if (osnoise_data.stop_tracing_total)
if (s.noise > osnoise_data.stop_tracing_total)
osnoise_stop_tracing();
return 0;
out:
return ret;
}
static struct cpumask osnoise_cpumask;
static struct cpumask save_cpumask;
/*
* osnoise_sleep - sleep until the next period
*/
static void osnoise_sleep(void)
{
u64 interval;
ktime_t wake_time;
mutex_lock(&interface_lock);
interval = osnoise_data.sample_period - osnoise_data.sample_runtime;
mutex_unlock(&interface_lock);
/*
* differently from hwlat_detector, the osnoise tracer can run
* without a pause because preemption is on.
*/
if (!interval) {
/* Let synchronize_rcu_tasks() make progress */
cond_resched_tasks_rcu_qs();
return;
}
wake_time = ktime_add_us(ktime_get(), interval);
__set_current_state(TASK_INTERRUPTIBLE);
while (schedule_hrtimeout_range(&wake_time, 0, HRTIMER_MODE_ABS)) {
if (kthread_should_stop())
break;
}
}
/*
* osnoise_main - The osnoise detection kernel thread
*
* Calls run_osnoise() function to measure the osnoise for the configured runtime,
* every period.
*/
static int osnoise_main(void *data)
{
while (!kthread_should_stop()) {
run_osnoise();
osnoise_sleep();
}
return 0;
}
#ifdef CONFIG_TIMERLAT_TRACER
/*
* timerlat_irq - hrtimer handler for timerlat.
*/
static enum hrtimer_restart timerlat_irq(struct hrtimer *timer)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
struct timerlat_variables *tlat;
struct timerlat_sample s;
u64 now;
u64 diff;
/*
* I am not sure if the timer was armed for this CPU. So, get
* the timerlat struct from the timer itself, not from this
* CPU.
*/
tlat = container_of(timer, struct timerlat_variables, timer);
now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
/*
* Enable the osnoise: events for thread an softirq.
*/
tlat->tracing_thread = true;
osn_var->thread.arrival_time = time_get();
/*
* A hardirq is running: the timer IRQ. It is for sure preempting
* a thread, and potentially preempting a softirq.
*
* At this point, it is not interesting to know the duration of the
* preempted thread (and maybe softirq), but how much time they will
* delay the beginning of the execution of the timer thread.
*
* To get the correct (net) delay added by the softirq, its delta_start
* is set as the IRQ one. In this way, at the return of the IRQ, the delta
* start of the sofitrq will be zeroed, accounting then only the time
* after that.
*
* The thread follows the same principle. However, if a softirq is
* running, the thread needs to receive the softirq delta_start. The
* reason being is that the softirq will be the last to be unfolded,
* resseting the thread delay to zero.
*
* The PREEMPT_RT is a special case, though. As softirqs run as threads
* on RT, moving the thread is enough.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT) && osn_var->softirq.delta_start) {
copy_int_safe_time(osn_var, &osn_var->thread.delta_start,
&osn_var->softirq.delta_start);
copy_int_safe_time(osn_var, &osn_var->softirq.delta_start,
&osn_var->irq.delta_start);
} else {
copy_int_safe_time(osn_var, &osn_var->thread.delta_start,
&osn_var->irq.delta_start);
}
/*
* Compute the current time with the expected time.
*/
diff = now - tlat->abs_period;
tlat->count++;
s.seqnum = tlat->count;
s.timer_latency = diff;
s.context = IRQ_CONTEXT;
trace_timerlat_sample(&s);
notify_new_max_latency(diff);
if (osnoise_data.stop_tracing)
if (time_to_us(diff) >= osnoise_data.stop_tracing)
osnoise_stop_tracing();
wake_up_process(tlat->kthread);
if (osnoise_data.print_stack)
timerlat_save_stack(0);
return HRTIMER_NORESTART;
}
/*
* wait_next_period - Wait for the next period for timerlat
*/
static int wait_next_period(struct timerlat_variables *tlat)
{
ktime_t next_abs_period, now;
u64 rel_period = osnoise_data.timerlat_period * 1000;
now = hrtimer_cb_get_time(&tlat->timer);
next_abs_period = ns_to_ktime(tlat->abs_period + rel_period);
/*
* Save the next abs_period.
*/
tlat->abs_period = (u64) ktime_to_ns(next_abs_period);
/*
* If the new abs_period is in the past, skip the activation.
*/
while (ktime_compare(now, next_abs_period) > 0) {
next_abs_period = ns_to_ktime(tlat->abs_period + rel_period);
tlat->abs_period = (u64) ktime_to_ns(next_abs_period);
}
set_current_state(TASK_INTERRUPTIBLE);
hrtimer_start(&tlat->timer, next_abs_period, HRTIMER_MODE_ABS_PINNED_HARD);
schedule();
return 1;
}
/*
* timerlat_main- Timerlat main
*/
static int timerlat_main(void *data)
{
struct osnoise_variables *osn_var = this_cpu_osn_var();
struct timerlat_variables *tlat = this_cpu_tmr_var();
struct timerlat_sample s;
struct sched_param sp;
u64 now, diff;
/*
* Make the thread RT, that is how cyclictest is usually used.
*/
sp.sched_priority = DEFAULT_TIMERLAT_PRIO;
sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
tlat->count = 0;
tlat->tracing_thread = false;
hrtimer_init(&tlat->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD);
tlat->timer.function = timerlat_irq;
tlat->kthread = current;
osn_var->pid = current->pid;
/*
* Anotate the arrival time.
*/
tlat->abs_period = hrtimer_cb_get_time(&tlat->timer);
wait_next_period(tlat);
osn_var->sampling = 1;
while (!kthread_should_stop()) {
now = ktime_to_ns(hrtimer_cb_get_time(&tlat->timer));
diff = now - tlat->abs_period;
s.seqnum = tlat->count;
s.timer_latency = diff;
s.context = THREAD_CONTEXT;
trace_timerlat_sample(&s);
timerlat_dump_stack(time_to_us(diff));
tlat->tracing_thread = false;
if (osnoise_data.stop_tracing_total)
if (time_to_us(diff) >= osnoise_data.stop_tracing_total)
osnoise_stop_tracing();
wait_next_period(tlat);
}
hrtimer_cancel(&tlat->timer);
return 0;
}
#else /* CONFIG_TIMERLAT_TRACER */
static int timerlat_main(void *data)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* stop_kthread - stop a workload thread
*/
static void stop_kthread(unsigned int cpu)
{
struct task_struct *kthread;
kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;
if (kthread)
kthread_stop(kthread);
per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
}
/*
* stop_per_cpu_kthread - Stop per-cpu threads
*
* Stop the osnoise sampling htread. Use this on unload and at system
* shutdown.
*/
static void stop_per_cpu_kthreads(void)
{
int cpu;
cpus_read_lock();
for_each_online_cpu(cpu)
stop_kthread(cpu);
cpus_read_unlock();
}
/*
* start_kthread - Start a workload tread
*/
static int start_kthread(unsigned int cpu)
{
struct task_struct *kthread;
void *main = osnoise_main;
char comm[24];
if (timerlat_enabled()) {
snprintf(comm, 24, "timerlat/%d", cpu);
main = timerlat_main;
} else {
snprintf(comm, 24, "osnoise/%d", cpu);
}
kthread = kthread_run_on_cpu(main, NULL, cpu, comm);
if (IS_ERR(kthread)) {
pr_err(BANNER "could not start sampling thread\n");
stop_per_cpu_kthreads();
return -ENOMEM;
}
per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;
return 0;
}
/*
* start_per_cpu_kthread - Kick off per-cpu osnoise sampling kthreads
*
* This starts the kernel thread that will look for osnoise on many
* cpus.
*/
static int start_per_cpu_kthreads(void)
{
struct cpumask *current_mask = &save_cpumask;
int retval = 0;
int cpu;
cpus_read_lock();
/*
* Run only on online CPUs in which osnoise is allowed to run.
*/
cpumask_and(current_mask, cpu_online_mask, &osnoise_cpumask);
for_each_possible_cpu(cpu)
per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;
for_each_cpu(cpu, current_mask) {
retval = start_kthread(cpu);
if (retval) {
stop_per_cpu_kthreads();
break;
}
}
cpus_read_unlock();
return retval;
}
#ifdef CONFIG_HOTPLUG_CPU
static void osnoise_hotplug_workfn(struct work_struct *dummy)
{
unsigned int cpu = smp_processor_id();
mutex_lock(&trace_types_lock);
if (!osnoise_has_registered_instances())
goto out_unlock_trace;
mutex_lock(&interface_lock);
cpus_read_lock();
if (!cpumask_test_cpu(cpu, &osnoise_cpumask))
goto out_unlock;
start_kthread(cpu);
out_unlock:
cpus_read_unlock();
mutex_unlock(&interface_lock);
out_unlock_trace:
mutex_unlock(&trace_types_lock);
}
static DECLARE_WORK(osnoise_hotplug_work, osnoise_hotplug_workfn);
/*
* osnoise_cpu_init - CPU hotplug online callback function
*/
static int osnoise_cpu_init(unsigned int cpu)
{
schedule_work_on(cpu, &osnoise_hotplug_work);
return 0;
}
/*
* osnoise_cpu_die - CPU hotplug offline callback function
*/
static int osnoise_cpu_die(unsigned int cpu)
{
stop_kthread(cpu);
return 0;
}
static void osnoise_init_hotplug_support(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/osnoise:online",
osnoise_cpu_init, osnoise_cpu_die);
if (ret < 0)
pr_warn(BANNER "Error to init cpu hotplug support\n");
return;
}
#else /* CONFIG_HOTPLUG_CPU */
static void osnoise_init_hotplug_support(void)
{
return;
}
#endif /* CONFIG_HOTPLUG_CPU */
/*
* osnoise_cpus_read - Read function for reading the "cpus" file
* @filp: The active open file structure
* @ubuf: The userspace provided buffer to read value into
* @cnt: The maximum number of bytes to read
* @ppos: The current "file" position
*
* Prints the "cpus" output into the user-provided buffer.
*/
static ssize_t
osnoise_cpus_read(struct file *filp, char __user *ubuf, size_t count,
loff_t *ppos)
{
char *mask_str;
int len;
mutex_lock(&interface_lock);
len = snprintf(NULL, 0, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask)) + 1;
mask_str = kmalloc(len, GFP_KERNEL);
if (!mask_str) {
count = -ENOMEM;
goto out_unlock;
}
len = snprintf(mask_str, len, "%*pbl\n", cpumask_pr_args(&osnoise_cpumask));
if (len >= count) {
count = -EINVAL;
goto out_free;
}
count = simple_read_from_buffer(ubuf, count, ppos, mask_str, len);
out_free:
kfree(mask_str);
out_unlock:
mutex_unlock(&interface_lock);
return count;
}
/*
* osnoise_cpus_write - Write function for "cpus" entry
* @filp: The active open file structure
* @ubuf: The user buffer that contains the value to write
* @cnt: The maximum number of bytes to write to "file"
* @ppos: The current position in @file
*
* This function provides a write implementation for the "cpus"
* interface to the osnoise trace. By default, it lists all CPUs,
* in this way, allowing osnoise threads to run on any online CPU
* of the system. It serves to restrict the execution of osnoise to the
* set of CPUs writing via this interface. Why not use "tracing_cpumask"?
* Because the user might be interested in tracing what is running on
* other CPUs. For instance, one might run osnoise in one HT CPU
* while observing what is running on the sibling HT CPU.
*/
static ssize_t
osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count,
loff_t *ppos)
{
cpumask_var_t osnoise_cpumask_new;
int running, err;
char buf[256];
if (count >= 256)
return -EINVAL;
if (copy_from_user(buf, ubuf, count))
return -EFAULT;
if (!zalloc_cpumask_var(&osnoise_cpumask_new, GFP_KERNEL))
return -ENOMEM;
err = cpulist_parse(buf, osnoise_cpumask_new);
if (err)
goto err_free;
/*
* trace_types_lock is taken to avoid concurrency on start/stop.
*/
mutex_lock(&trace_types_lock);
running = osnoise_has_registered_instances();
if (running)
stop_per_cpu_kthreads();
mutex_lock(&interface_lock);
/*
* osnoise_cpumask is read by CPU hotplug operations.
*/
cpus_read_lock();
cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);
cpus_read_unlock();
mutex_unlock(&interface_lock);
if (running)
start_per_cpu_kthreads();
mutex_unlock(&trace_types_lock);
free_cpumask_var(osnoise_cpumask_new);
return count;
err_free:
free_cpumask_var(osnoise_cpumask_new);
return err;
}
/*
* osnoise/runtime_us: cannot be greater than the period.
*/
static struct trace_min_max_param osnoise_runtime = {
.lock = &interface_lock,
.val = &osnoise_data.sample_runtime,
.max = &osnoise_data.sample_period,
.min = NULL,
};
/*
* osnoise/period_us: cannot be smaller than the runtime.
*/
static struct trace_min_max_param osnoise_period = {
.lock = &interface_lock,
.val = &osnoise_data.sample_period,
.max = NULL,
.min = &osnoise_data.sample_runtime,
};
/*
* osnoise/stop_tracing_us: no limit.
*/
static struct trace_min_max_param osnoise_stop_tracing_in = {
.lock = &interface_lock,
.val = &osnoise_data.stop_tracing,
.max = NULL,
.min = NULL,
};
/*
* osnoise/stop_tracing_total_us: no limit.
*/
static struct trace_min_max_param osnoise_stop_tracing_total = {
.lock = &interface_lock,
.val = &osnoise_data.stop_tracing_total,
.max = NULL,
.min = NULL,
};
#ifdef CONFIG_TIMERLAT_TRACER
/*
* osnoise/print_stack: print the stacktrace of the IRQ handler if the total
* latency is higher than val.
*/
static struct trace_min_max_param osnoise_print_stack = {
.lock = &interface_lock,
.val = &osnoise_data.print_stack,
.max = NULL,
.min = NULL,
};
/*
* osnoise/timerlat_period: min 100 us, max 1 s
*/
u64 timerlat_min_period = 100;
u64 timerlat_max_period = 1000000;
static struct trace_min_max_param timerlat_period = {
.lock = &interface_lock,
.val = &osnoise_data.timerlat_period,
.max = &timerlat_max_period,
.min = &timerlat_min_period,
};
#endif
static const struct file_operations cpus_fops = {
.open = tracing_open_generic,
.read = osnoise_cpus_read,
.write = osnoise_cpus_write,
.llseek = generic_file_llseek,
};
#ifdef CONFIG_TIMERLAT_TRACER
#ifdef CONFIG_STACKTRACE
static int init_timerlat_stack_tracefs(struct dentry *top_dir)
{
struct dentry *tmp;
tmp = tracefs_create_file("print_stack", TRACE_MODE_WRITE, top_dir,
&osnoise_print_stack, &trace_min_max_fops);
if (!tmp)
return -ENOMEM;
return 0;
}
#else /* CONFIG_STACKTRACE */
static int init_timerlat_stack_tracefs(struct dentry *top_dir)
{
return 0;
}
#endif /* CONFIG_STACKTRACE */
/*
* init_timerlat_tracefs - A function to initialize the timerlat interface files
*/
static int init_timerlat_tracefs(struct dentry *top_dir)
{
struct dentry *tmp;
tmp = tracefs_create_file("timerlat_period_us", TRACE_MODE_WRITE, top_dir,
&timerlat_period, &trace_min_max_fops);
if (!tmp)
return -ENOMEM;
return init_timerlat_stack_tracefs(top_dir);
}
#else /* CONFIG_TIMERLAT_TRACER */
static int init_timerlat_tracefs(struct dentry *top_dir)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
/*
* init_tracefs - A function to initialize the tracefs interface files
*
* This function creates entries in tracefs for "osnoise" and "timerlat".
* It creates these directories in the tracing directory, and within that
* directory the use can change and view the configs.
*/
static int init_tracefs(void)
{
struct dentry *top_dir;
struct dentry *tmp;
int ret;
ret = tracing_init_dentry();
if (ret)
return -ENOMEM;
top_dir = tracefs_create_dir("osnoise", NULL);
if (!top_dir)
return 0;
tmp = tracefs_create_file("period_us", TRACE_MODE_WRITE, top_dir,
&osnoise_period, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("runtime_us", TRACE_MODE_WRITE, top_dir,
&osnoise_runtime, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("stop_tracing_us", TRACE_MODE_WRITE, top_dir,
&osnoise_stop_tracing_in, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = tracefs_create_file("stop_tracing_total_us", TRACE_MODE_WRITE, top_dir,
&osnoise_stop_tracing_total, &trace_min_max_fops);
if (!tmp)
goto err;
tmp = trace_create_file("cpus", TRACE_MODE_WRITE, top_dir, NULL, &cpus_fops);
if (!tmp)
goto err;
ret = init_timerlat_tracefs(top_dir);
if (ret)
goto err;
return 0;
err:
tracefs_remove(top_dir);
return -ENOMEM;
}
static int osnoise_hook_events(void)
{
int retval;
/*
* Trace is already hooked, we are re-enabling from
* a stop_tracing_*.
*/
if (trace_osnoise_callback_enabled)
return 0;
retval = hook_irq_events();
if (retval)
return -EINVAL;
retval = hook_softirq_events();
if (retval)
goto out_unhook_irq;
retval = hook_thread_events();
/*
* All fine!
*/
if (!retval)
return 0;
unhook_softirq_events();
out_unhook_irq:
unhook_irq_events();
return -EINVAL;
}
static void osnoise_unhook_events(void)
{
unhook_thread_events();
unhook_softirq_events();
unhook_irq_events();
}
/*
* osnoise_workload_start - start the workload and hook to events
*/
static int osnoise_workload_start(void)
{
int retval;
/*
* Instances need to be registered after calling workload
* start. Hence, if there is already an instance, the
* workload was already registered. Otherwise, this
* code is on the way to register the first instance,
* and the workload will start.
*/
if (osnoise_has_registered_instances())
return 0;
osn_var_reset_all();
retval = osnoise_hook_events();
if (retval)
return retval;
/*
* Make sure that ftrace_nmi_enter/exit() see reset values
* before enabling trace_osnoise_callback_enabled.
*/
barrier();
trace_osnoise_callback_enabled = true;
retval = start_per_cpu_kthreads();
if (retval) {
trace_osnoise_callback_enabled = false;
/*
* Make sure that ftrace_nmi_enter/exit() see
* trace_osnoise_callback_enabled as false before continuing.
*/
barrier();
osnoise_unhook_events();
return retval;
}
return 0;
}
/*
* osnoise_workload_stop - stop the workload and unhook the events
*/
static void osnoise_workload_stop(void)
{
/*
* Instances need to be unregistered before calling
* stop. Hence, if there is a registered instance, more
* than one instance is running, and the workload will not
* yet stop. Otherwise, this code is on the way to disable
* the last instance, and the workload can stop.
*/
if (osnoise_has_registered_instances())
return;
trace_osnoise_callback_enabled = false;
/*
* Make sure that ftrace_nmi_enter/exit() see
* trace_osnoise_callback_enabled as false before continuing.
*/
barrier();
stop_per_cpu_kthreads();
osnoise_unhook_events();
}
static void osnoise_tracer_start(struct trace_array *tr)
{
int retval;
/*
* If the instance is already registered, there is no need to
* register it again.
*/
if (osnoise_instance_registered(tr))
return;
retval = osnoise_workload_start();
if (retval)
pr_err(BANNER "Error starting osnoise tracer\n");
osnoise_register_instance(tr);
}
static void osnoise_tracer_stop(struct trace_array *tr)
{
osnoise_unregister_instance(tr);
osnoise_workload_stop();
}
static int osnoise_tracer_init(struct trace_array *tr)
{
/*
* Only allow osnoise tracer if timerlat tracer is not running
* already.
*/
if (timerlat_enabled())
return -EBUSY;
tr->max_latency = 0;
osnoise_tracer_start(tr);
return 0;
}
static void osnoise_tracer_reset(struct trace_array *tr)
{
osnoise_tracer_stop(tr);
}
static struct tracer osnoise_tracer __read_mostly = {
.name = "osnoise",
.init = osnoise_tracer_init,
.reset = osnoise_tracer_reset,
.start = osnoise_tracer_start,
.stop = osnoise_tracer_stop,
.print_header = print_osnoise_headers,
.allow_instances = true,
};
#ifdef CONFIG_TIMERLAT_TRACER
static void timerlat_tracer_start(struct trace_array *tr)
{
int retval;
/*
* If the instance is already registered, there is no need to
* register it again.
*/
if (osnoise_instance_registered(tr))
return;
retval = osnoise_workload_start();
if (retval)
pr_err(BANNER "Error starting timerlat tracer\n");
osnoise_register_instance(tr);
return;
}
static void timerlat_tracer_stop(struct trace_array *tr)
{
int cpu;
osnoise_unregister_instance(tr);
/*
* Instruct the threads to stop only if this is the last instance.
*/
if (!osnoise_has_registered_instances()) {
for_each_online_cpu(cpu)
per_cpu(per_cpu_osnoise_var, cpu).sampling = 0;
}
osnoise_workload_stop();
}
static int timerlat_tracer_init(struct trace_array *tr)
{
/*
* Only allow timerlat tracer if osnoise tracer is not running already.
*/
if (osnoise_has_registered_instances() && !osnoise_data.timerlat_tracer)
return -EBUSY;
/*
* If this is the first instance, set timerlat_tracer to block
* osnoise tracer start.
*/
if (!osnoise_has_registered_instances())
osnoise_data.timerlat_tracer = 1;
tr->max_latency = 0;
timerlat_tracer_start(tr);
return 0;
}
static void timerlat_tracer_reset(struct trace_array *tr)
{
timerlat_tracer_stop(tr);
/*
* If this is the last instance, reset timerlat_tracer allowing
* osnoise to be started.
*/
if (!osnoise_has_registered_instances())
osnoise_data.timerlat_tracer = 0;
}
static struct tracer timerlat_tracer __read_mostly = {
.name = "timerlat",
.init = timerlat_tracer_init,
.reset = timerlat_tracer_reset,
.start = timerlat_tracer_start,
.stop = timerlat_tracer_stop,
.print_header = print_timerlat_headers,
.allow_instances = true,
};
__init static int init_timerlat_tracer(void)
{
return register_tracer(&timerlat_tracer);
}
#else /* CONFIG_TIMERLAT_TRACER */
__init static int init_timerlat_tracer(void)
{
return 0;
}
#endif /* CONFIG_TIMERLAT_TRACER */
__init static int init_osnoise_tracer(void)
{
int ret;
mutex_init(&interface_lock);
cpumask_copy(&osnoise_cpumask, cpu_all_mask);
ret = register_tracer(&osnoise_tracer);
if (ret) {
pr_err(BANNER "Error registering osnoise!\n");
return ret;
}
ret = init_timerlat_tracer();
if (ret) {
pr_err(BANNER "Error registering timerlat!\n");
return ret;
}
osnoise_init_hotplug_support();
INIT_LIST_HEAD_RCU(&osnoise_instances);
init_tracefs();
return 0;
}
late_initcall(init_osnoise_tracer);
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