linux/kernel/trace/trace_sched_wakeup.c
Steven Rostedt 3244351c31 trace: separate out rt tasks from wakeup tracer
Impact: add option to trace all tasks or just RT tasks

The current wakeup tracer only traces RT task wakeups. This is
fine for those interested in wake up timings of RT tasks, but
it is useless for those that are interested in the causes
of long wakeups for non RT tasks.

This patch creates a "wakeup_rt" to implement the tracing of just
RT tasks (as the current "wakeup" does). And makes "wakeup" now
trace all tasks as an average developer would expect.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-01-22 10:27:22 +01:00

404 lines
8.5 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, data, 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, data, CALLER_ADDR1, CALLER_ADDR2, 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)
{
struct trace_array_cpu *data;
int cpu;
for_each_possible_cpu(cpu) {
data = tr->data[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)
{
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);
wakeup_trace->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu);
trace_function(wakeup_trace, wakeup_trace->data[wakeup_cpu],
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_schedule\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,
.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);