/*
* 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 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 = need_resched();
preempt_disable_notrace();
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);
/*
* To prevent recursion from the scheduler, if the
* resched flag was set before we entered, then
* don't reschedule.
*/
if (resched)
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
}
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 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 (likely(!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);
tracer_enabled = 1;
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 void wakeup_tracer_init(struct trace_array *tr)
{
wakeup_trace = tr;
if (tr->ctrl)
start_wakeup_tracer(tr);
}
static void wakeup_tracer_reset(struct trace_array *tr)
{
if (tr->ctrl) {
stop_wakeup_tracer(tr);
/* make sure we put back any tasks we are tracing */
wakeup_reset(tr);
}
}
static void wakeup_tracer_ctrl_update(struct trace_array *tr)
{
if (tr->ctrl)
start_wakeup_tracer(tr);
else
stop_wakeup_tracer(tr);
}
static void wakeup_tracer_open(struct trace_iterator *iter)
{
/* stop the trace while dumping */
if (iter->tr->ctrl)
stop_wakeup_tracer(iter->tr);
}
static void wakeup_tracer_close(struct trace_iterator *iter)
{
/* forget about any processes we were recording */
if (iter->tr->ctrl)
start_wakeup_tracer(iter->tr);
}
static struct tracer wakeup_tracer __read_mostly =
{
.name = "wakeup",
.init = wakeup_tracer_init,
.reset = wakeup_tracer_reset,
.open = wakeup_tracer_open,
.close = wakeup_tracer_close,
.ctrl_update = wakeup_tracer_ctrl_update,
.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;
return 0;
}
device_initcall(init_wakeup_tracer);
