mirror of
https://github.com/torvalds/linux
synced 2024-09-22 12:26:27 +00:00
6eaaa5d57e
Impact: api and pipe waiting change Currently, the waiting used in tracing_read_pipe() is done through a 100 msecs schedule_timeout() loop which periodically check if there are traces on the buffer. This can cause small latencies for programs which are reading the incoming events. This patch makes the reader waiting for the trace_wait waitqueue except for few tracers such as the sched and functions tracers which might be already hold the runqueue lock while waking up the reader. This is performed through a new callback wait_pipe() on struct tracer. If none is implemented on a specific tracer, the default waiting for trace_wait queue is attached. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
405 lines
8.6 KiB
C
405 lines
8.6 KiB
C
/*
|
|
* trace task wakeup timings
|
|
*
|
|
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
|
|
* Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
|
|
*
|
|
* Based on code from the latency_tracer, that is:
|
|
*
|
|
* Copyright (C) 2004-2006 Ingo Molnar
|
|
* Copyright (C) 2004 William Lee Irwin III
|
|
*/
|
|
#include <linux/module.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/debugfs.h>
|
|
#include <linux/kallsyms.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/ftrace.h>
|
|
#include <trace/sched.h>
|
|
|
|
#include "trace.h"
|
|
|
|
static struct trace_array *wakeup_trace;
|
|
static int __read_mostly tracer_enabled;
|
|
|
|
static struct task_struct *wakeup_task;
|
|
static int wakeup_cpu;
|
|
static unsigned wakeup_prio = -1;
|
|
static int wakeup_rt;
|
|
|
|
static raw_spinlock_t wakeup_lock =
|
|
(raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
|
|
|
|
static void __wakeup_reset(struct trace_array *tr);
|
|
|
|
#ifdef CONFIG_FUNCTION_TRACER
|
|
/*
|
|
* irqsoff uses its own tracer function to keep the overhead down:
|
|
*/
|
|
static void
|
|
wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
|
|
{
|
|
struct trace_array *tr = wakeup_trace;
|
|
struct trace_array_cpu *data;
|
|
unsigned long flags;
|
|
long disabled;
|
|
int resched;
|
|
int cpu;
|
|
int pc;
|
|
|
|
if (likely(!wakeup_task))
|
|
return;
|
|
|
|
pc = preempt_count();
|
|
resched = ftrace_preempt_disable();
|
|
|
|
cpu = raw_smp_processor_id();
|
|
data = tr->data[cpu];
|
|
disabled = atomic_inc_return(&data->disabled);
|
|
if (unlikely(disabled != 1))
|
|
goto out;
|
|
|
|
local_irq_save(flags);
|
|
__raw_spin_lock(&wakeup_lock);
|
|
|
|
if (unlikely(!wakeup_task))
|
|
goto unlock;
|
|
|
|
/*
|
|
* The task can't disappear because it needs to
|
|
* wake up first, and we have the wakeup_lock.
|
|
*/
|
|
if (task_cpu(wakeup_task) != cpu)
|
|
goto unlock;
|
|
|
|
trace_function(tr, ip, parent_ip, flags, pc);
|
|
|
|
unlock:
|
|
__raw_spin_unlock(&wakeup_lock);
|
|
local_irq_restore(flags);
|
|
|
|
out:
|
|
atomic_dec(&data->disabled);
|
|
|
|
ftrace_preempt_enable(resched);
|
|
}
|
|
|
|
static struct ftrace_ops trace_ops __read_mostly =
|
|
{
|
|
.func = wakeup_tracer_call,
|
|
};
|
|
#endif /* CONFIG_FUNCTION_TRACER */
|
|
|
|
/*
|
|
* Should this new latency be reported/recorded?
|
|
*/
|
|
static int report_latency(cycle_t delta)
|
|
{
|
|
if (tracing_thresh) {
|
|
if (delta < tracing_thresh)
|
|
return 0;
|
|
} else {
|
|
if (delta <= tracing_max_latency)
|
|
return 0;
|
|
}
|
|
return 1;
|
|
}
|
|
|
|
static void notrace
|
|
probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
|
|
struct task_struct *next)
|
|
{
|
|
unsigned long latency = 0, t0 = 0, t1 = 0;
|
|
struct trace_array_cpu *data;
|
|
cycle_t T0, T1, delta;
|
|
unsigned long flags;
|
|
long disabled;
|
|
int cpu;
|
|
int pc;
|
|
|
|
tracing_record_cmdline(prev);
|
|
|
|
if (unlikely(!tracer_enabled))
|
|
return;
|
|
|
|
/*
|
|
* When we start a new trace, we set wakeup_task to NULL
|
|
* and then set tracer_enabled = 1. We want to make sure
|
|
* that another CPU does not see the tracer_enabled = 1
|
|
* and the wakeup_task with an older task, that might
|
|
* actually be the same as next.
|
|
*/
|
|
smp_rmb();
|
|
|
|
if (next != wakeup_task)
|
|
return;
|
|
|
|
pc = preempt_count();
|
|
|
|
/* The task we are waiting for is waking up */
|
|
data = wakeup_trace->data[wakeup_cpu];
|
|
|
|
/* disable local data, not wakeup_cpu data */
|
|
cpu = raw_smp_processor_id();
|
|
disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
|
|
if (likely(disabled != 1))
|
|
goto out;
|
|
|
|
local_irq_save(flags);
|
|
__raw_spin_lock(&wakeup_lock);
|
|
|
|
/* We could race with grabbing wakeup_lock */
|
|
if (unlikely(!tracer_enabled || next != wakeup_task))
|
|
goto out_unlock;
|
|
|
|
trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
|
|
tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
|
|
|
|
/*
|
|
* usecs conversion is slow so we try to delay the conversion
|
|
* as long as possible:
|
|
*/
|
|
T0 = data->preempt_timestamp;
|
|
T1 = ftrace_now(cpu);
|
|
delta = T1-T0;
|
|
|
|
if (!report_latency(delta))
|
|
goto out_unlock;
|
|
|
|
latency = nsecs_to_usecs(delta);
|
|
|
|
tracing_max_latency = delta;
|
|
t0 = nsecs_to_usecs(T0);
|
|
t1 = nsecs_to_usecs(T1);
|
|
|
|
update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
|
|
|
|
out_unlock:
|
|
__wakeup_reset(wakeup_trace);
|
|
__raw_spin_unlock(&wakeup_lock);
|
|
local_irq_restore(flags);
|
|
out:
|
|
atomic_dec(&wakeup_trace->data[cpu]->disabled);
|
|
}
|
|
|
|
static void __wakeup_reset(struct trace_array *tr)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_possible_cpu(cpu)
|
|
tracing_reset(tr, cpu);
|
|
|
|
wakeup_cpu = -1;
|
|
wakeup_prio = -1;
|
|
|
|
if (wakeup_task)
|
|
put_task_struct(wakeup_task);
|
|
|
|
wakeup_task = NULL;
|
|
}
|
|
|
|
static void wakeup_reset(struct trace_array *tr)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
__raw_spin_lock(&wakeup_lock);
|
|
__wakeup_reset(tr);
|
|
__raw_spin_unlock(&wakeup_lock);
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
static void
|
|
probe_wakeup(struct rq *rq, struct task_struct *p, int success)
|
|
{
|
|
struct trace_array_cpu *data;
|
|
int cpu = smp_processor_id();
|
|
unsigned long flags;
|
|
long disabled;
|
|
int pc;
|
|
|
|
if (likely(!tracer_enabled))
|
|
return;
|
|
|
|
tracing_record_cmdline(p);
|
|
tracing_record_cmdline(current);
|
|
|
|
if ((wakeup_rt && !rt_task(p)) ||
|
|
p->prio >= wakeup_prio ||
|
|
p->prio >= current->prio)
|
|
return;
|
|
|
|
pc = preempt_count();
|
|
disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
|
|
if (unlikely(disabled != 1))
|
|
goto out;
|
|
|
|
/* interrupts should be off from try_to_wake_up */
|
|
__raw_spin_lock(&wakeup_lock);
|
|
|
|
/* check for races. */
|
|
if (!tracer_enabled || p->prio >= wakeup_prio)
|
|
goto out_locked;
|
|
|
|
/* reset the trace */
|
|
__wakeup_reset(wakeup_trace);
|
|
|
|
wakeup_cpu = task_cpu(p);
|
|
wakeup_prio = p->prio;
|
|
|
|
wakeup_task = p;
|
|
get_task_struct(wakeup_task);
|
|
|
|
local_save_flags(flags);
|
|
|
|
data = wakeup_trace->data[wakeup_cpu];
|
|
data->preempt_timestamp = ftrace_now(cpu);
|
|
tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
|
|
trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
|
|
|
|
out_locked:
|
|
__raw_spin_unlock(&wakeup_lock);
|
|
out:
|
|
atomic_dec(&wakeup_trace->data[cpu]->disabled);
|
|
}
|
|
|
|
static void start_wakeup_tracer(struct trace_array *tr)
|
|
{
|
|
int ret;
|
|
|
|
ret = register_trace_sched_wakeup(probe_wakeup);
|
|
if (ret) {
|
|
pr_info("wakeup trace: Couldn't activate tracepoint"
|
|
" probe to kernel_sched_wakeup\n");
|
|
return;
|
|
}
|
|
|
|
ret = register_trace_sched_wakeup_new(probe_wakeup);
|
|
if (ret) {
|
|
pr_info("wakeup trace: Couldn't activate tracepoint"
|
|
" probe to kernel_sched_wakeup_new\n");
|
|
goto fail_deprobe;
|
|
}
|
|
|
|
ret = register_trace_sched_switch(probe_wakeup_sched_switch);
|
|
if (ret) {
|
|
pr_info("sched trace: Couldn't activate tracepoint"
|
|
" probe to kernel_sched_switch\n");
|
|
goto fail_deprobe_wake_new;
|
|
}
|
|
|
|
wakeup_reset(tr);
|
|
|
|
/*
|
|
* Don't let the tracer_enabled = 1 show up before
|
|
* the wakeup_task is reset. This may be overkill since
|
|
* wakeup_reset does a spin_unlock after setting the
|
|
* wakeup_task to NULL, but I want to be safe.
|
|
* This is a slow path anyway.
|
|
*/
|
|
smp_wmb();
|
|
|
|
register_ftrace_function(&trace_ops);
|
|
|
|
if (tracing_is_enabled())
|
|
tracer_enabled = 1;
|
|
else
|
|
tracer_enabled = 0;
|
|
|
|
return;
|
|
fail_deprobe_wake_new:
|
|
unregister_trace_sched_wakeup_new(probe_wakeup);
|
|
fail_deprobe:
|
|
unregister_trace_sched_wakeup(probe_wakeup);
|
|
}
|
|
|
|
static void stop_wakeup_tracer(struct trace_array *tr)
|
|
{
|
|
tracer_enabled = 0;
|
|
unregister_ftrace_function(&trace_ops);
|
|
unregister_trace_sched_switch(probe_wakeup_sched_switch);
|
|
unregister_trace_sched_wakeup_new(probe_wakeup);
|
|
unregister_trace_sched_wakeup(probe_wakeup);
|
|
}
|
|
|
|
static int __wakeup_tracer_init(struct trace_array *tr)
|
|
{
|
|
tracing_max_latency = 0;
|
|
wakeup_trace = tr;
|
|
start_wakeup_tracer(tr);
|
|
return 0;
|
|
}
|
|
|
|
static int wakeup_tracer_init(struct trace_array *tr)
|
|
{
|
|
wakeup_rt = 0;
|
|
return __wakeup_tracer_init(tr);
|
|
}
|
|
|
|
static int wakeup_rt_tracer_init(struct trace_array *tr)
|
|
{
|
|
wakeup_rt = 1;
|
|
return __wakeup_tracer_init(tr);
|
|
}
|
|
|
|
static void wakeup_tracer_reset(struct trace_array *tr)
|
|
{
|
|
stop_wakeup_tracer(tr);
|
|
/* make sure we put back any tasks we are tracing */
|
|
wakeup_reset(tr);
|
|
}
|
|
|
|
static void wakeup_tracer_start(struct trace_array *tr)
|
|
{
|
|
wakeup_reset(tr);
|
|
tracer_enabled = 1;
|
|
}
|
|
|
|
static void wakeup_tracer_stop(struct trace_array *tr)
|
|
{
|
|
tracer_enabled = 0;
|
|
}
|
|
|
|
static struct tracer wakeup_tracer __read_mostly =
|
|
{
|
|
.name = "wakeup",
|
|
.init = wakeup_tracer_init,
|
|
.reset = wakeup_tracer_reset,
|
|
.start = wakeup_tracer_start,
|
|
.stop = wakeup_tracer_stop,
|
|
.print_max = 1,
|
|
#ifdef CONFIG_FTRACE_SELFTEST
|
|
.selftest = trace_selftest_startup_wakeup,
|
|
#endif
|
|
};
|
|
|
|
static struct tracer wakeup_rt_tracer __read_mostly =
|
|
{
|
|
.name = "wakeup_rt",
|
|
.init = wakeup_rt_tracer_init,
|
|
.reset = wakeup_tracer_reset,
|
|
.start = wakeup_tracer_start,
|
|
.stop = wakeup_tracer_stop,
|
|
.wait_pipe = poll_wait_pipe,
|
|
.print_max = 1,
|
|
#ifdef CONFIG_FTRACE_SELFTEST
|
|
.selftest = trace_selftest_startup_wakeup,
|
|
#endif
|
|
};
|
|
|
|
__init static int init_wakeup_tracer(void)
|
|
{
|
|
int ret;
|
|
|
|
ret = register_tracer(&wakeup_tracer);
|
|
if (ret)
|
|
return ret;
|
|
|
|
ret = register_tracer(&wakeup_rt_tracer);
|
|
if (ret)
|
|
return ret;
|
|
|
|
return 0;
|
|
}
|
|
device_initcall(init_wakeup_tracer);
|