kernel/trace/trace_sysprof.c

/*
 * trace stack traces
 *
 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
 *
 */
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/hrtimer.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/fs.h>

#include "trace.h"

static struct trace_array	*ctx_trace;
static int __read_mostly	tracer_enabled;

static const unsigned long sample_period = 1000000;

/*
 * Per CPU hrtimers that do the profiling:
 */
static DEFINE_PER_CPU(struct hrtimer, stack_trace_hrtimer);

static enum hrtimer_restart stack_trace_timer_fn(struct hrtimer *hrtimer)
{
	/* trace here */
	panic_timeout++;

	hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));

	return HRTIMER_RESTART;
}

static void start_stack_timer(int cpu)
{
	struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);

	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
	hrtimer->function = stack_trace_timer_fn;
	hrtimer->cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;

	hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL);
}

static void start_stack_timers(void)
{
	cpumask_t saved_mask = current->cpus_allowed;
	int cpu;

	for_each_online_cpu(cpu) {
		set_cpus_allowed_ptr(current, &cpumask_of_cpu(cpu));
		start_stack_timer(cpu);
		printk("started timer on cpu%d\n", cpu);
	}
	set_cpus_allowed_ptr(current, &saved_mask);
}

static void stop_stack_timer(int cpu)
{
	struct hrtimer *hrtimer = &per_cpu(stack_trace_hrtimer, cpu);

	hrtimer_cancel(hrtimer);
	printk("cancelled timer on cpu%d\n", cpu);
}

static void stop_stack_timers(void)
{
	int cpu;

	for_each_online_cpu(cpu)
		stop_stack_timer(cpu);
}

static notrace void stack_reset(struct trace_array *tr)
{
	int cpu;

	tr->time_start = ftrace_now(tr->cpu);

	for_each_online_cpu(cpu)
		tracing_reset(tr->data[cpu]);
}

static notrace void start_stack_trace(struct trace_array *tr)
{
	stack_reset(tr);
	start_stack_timers();
	tracer_enabled = 1;
}

static notrace void stop_stack_trace(struct trace_array *tr)
{
	stop_stack_timers();
	tracer_enabled = 0;
}

static notrace void stack_trace_init(struct trace_array *tr)
{
	ctx_trace = tr;

	if (tr->ctrl)
		start_stack_trace(tr);
}

static notrace void stack_trace_reset(struct trace_array *tr)
{
	if (tr->ctrl)
		stop_stack_trace(tr);
}

static void stack_trace_ctrl_update(struct trace_array *tr)
{
	/* When starting a new trace, reset the buffers */
	if (tr->ctrl)
		start_stack_trace(tr);
	else
		stop_stack_trace(tr);
}

static struct tracer stack_trace __read_mostly =
{
	.name		= "sysprof",
	.init		= stack_trace_init,
	.reset		= stack_trace_reset,
	.ctrl_update	= stack_trace_ctrl_update,
#ifdef CONFIG_FTRACE_SELFTEST
	.selftest    = trace_selftest_startup_stack,
#endif
};

__init static int init_stack_trace(void)
{
	return register_tracer(&stack_trace);
}
device_initcall(init_stack_trace);