kernel/trace/trace_sched_wakeup.c - linux - Git at Google

 /*
  * 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(struct task_struct *task, int cpu)
 {
 	if (task != wakeup_task)
 		return;

 	wakeup_current_cpu = cpu;
 }

 static void notrace
 probe_wakeup_sched_switch(struct rq *rq, 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(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 */
 	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);
 	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;
 	}

 	ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task);
 	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);
 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);
 	unregister_trace_sched_migrate_task(probe_wakeup_migrate_task);
 }

 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);
	/*
	* 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(struct task_struct *task, int cpu)
	{
	if (task != wakeup_task)
	return;

	wakeup_current_cpu = cpu;
	}

	static void notrace
	probe_wakeup_sched_switch(struct rq rq, 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(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 */
	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);
	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;
	}

	ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task);
	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);
	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);
	unregister_trace_sched_migrate_task(probe_wakeup_migrate_task);
	}

	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);