/*
* 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/events/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 int wakeup_current_cpu;
static unsigned wakeup_prio = -1;
static int wakeup_rt;
static arch_spinlock_t wakeup_lock =
(arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
static void __wakeup_reset(struct trace_array *tr);
static int save_lat_flag;
#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();
if (cpu != wakeup_current_cpu)
goto out_enable;
data = tr->data[cpu];
disabled = atomic_inc_return(&data->disabled);
if (unlikely(disabled != 1))
goto out;
local_irq_save(flags);
trace_function(tr, ip, parent_ip, flags, pc);
local_irq_restore(flags);
out:
atomic_dec(&data->disabled);
out_enable:
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
probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
{
if (task != wakeup_task)
return;
wakeup_current_cpu = cpu;
}
static void notrace
probe_wakeup_sched_switch(void *ignore,
struct task_struct *prev, struct task_struct *next)
{
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();
/* 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);
arch_spin_lock(&wakeup_lock);
/* We could race with grabbing wakeup_lock */
if (unlikely(!tracer_enabled || next != wakeup_task))
goto out_unlock;
/* The task we are waiting for is waking up */
data = wakeup_trace->data[wakeup_cpu];
trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
T0 = data->preempt_timestamp;
T1 = ftrace_now(cpu);
delta = T1-T0;
if (!report_latency(delta))
goto out_unlock;
if (likely(!is_tracing_stopped())) {
tracing_max_latency = delta;
update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
}
out_unlock:
__wakeup_reset(wakeup_trace);
arch_spin_unlock(&wakeup_lock);
local_irq_restore(flags);
out:
atomic_dec(&wakeup_trace->data[cpu]->disabled);
}
static void __wakeup_reset(struct trace_array *tr)
{
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;
tracing_reset_online_cpus(tr);
local_irq_save(flags);
arch_spin_lock(&wakeup_lock);
__wakeup_reset(tr);
arch_spin_unlock(&wakeup_lock);
local_irq_restore(flags);
}
static void
probe_wakeup(void *ignore, 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 */
arch_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_current_cpu = wakeup_cpu;
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);
/*
* We must be careful in using CALLER_ADDR2. But since wake_up
* is not called by an assembly function (where as schedule is)
* it should be safe to use it here.
*/
trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
out_locked:
arch_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, NULL);
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, NULL);
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, NULL);
if (ret) {
pr_info("sched trace: Couldn't activate tracepoint"
" probe to kernel_sched_switch\n");
goto fail_deprobe_wake_new;
}
ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
if (ret) {
pr_info("wakeup trace: Couldn't activate tracepoint"
" probe to kernel_sched_migrate_task\n");
return;
}
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, NULL);
fail_deprobe:
unregister_trace_sched_wakeup(probe_wakeup, NULL);
}
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, NULL);
unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
unregister_trace_sched_wakeup(probe_wakeup, NULL);
unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
}
static int __wakeup_tracer_init(struct trace_array *tr)
{
save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
trace_flags |= TRACE_ITER_LATENCY_FMT;
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);
if (!save_lat_flag)
trace_flags &= ~TRACE_ITER_LATENCY_FMT;
}
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);
