root/kernel/trace/trace_sched_switch.c

DEFINITIONS

1. sched_switch_func
2. sched_switch_callback
3. wakeup_func
4. wake_up_callback
5. sched_switch_reset
6. tracing_sched_register
7. tracing_sched_unregister
8. tracing_start_sched_switch
9. tracing_stop_sched_switch
10. tracing_start_cmdline_record
11. tracing_stop_cmdline_record
12. start_sched_trace
13. stop_sched_trace
14. sched_switch_trace_init
15. sched_switch_trace_reset
16. sched_switch_trace_ctrl_update
17. init_sched_switch_trace

/*
 * trace context switch
 *
 * Copyright (C) 2007 Steven Rostedt <srostedt@redhat.com>
 *
 */
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
#include <linux/marker.h>
#include <linux/ftrace.h>

#include "trace.h"

static struct trace_array       *ctx_trace;
static int __read_mostly        tracer_enabled;
static atomic_t                 sched_ref;

static void
sched_switch_func(void *private, void *__rq, struct task_struct *prev,
                        struct task_struct *next)
{
        struct trace_array **ptr = private;
        struct trace_array *tr = *ptr;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int cpu;

        tracing_record_cmdline(prev);
        tracing_record_cmdline(next);

        if (!tracer_enabled)
                return;

        local_irq_save(flags);
        cpu = raw_smp_processor_id();
        data = tr->data[cpu];
        disabled = atomic_inc_return(&data->disabled);

        if (likely(disabled == 1))
                tracing_sched_switch_trace(tr, data, prev, next, flags);

        atomic_dec(&data->disabled);
        local_irq_restore(flags);
}

static notrace void
sched_switch_callback(void *probe_data, void *call_data,
                      const char *format, va_list *args)
{
        struct task_struct *prev;
        struct task_struct *next;
        struct rq *__rq;

        if (!atomic_read(&sched_ref))
                return;

        /* skip prev_pid %d next_pid %d prev_state %ld */
        (void)va_arg(*args, int);
        (void)va_arg(*args, int);
        (void)va_arg(*args, long);
        __rq = va_arg(*args, typeof(__rq));
        prev = va_arg(*args, typeof(prev));
        next = va_arg(*args, typeof(next));

        /*
         * If tracer_switch_func only points to the local
         * switch func, it still needs the ptr passed to it.
         */
        sched_switch_func(probe_data, __rq, prev, next);
}

static void
wakeup_func(void *private, void *__rq, struct task_struct *wakee, struct
                        task_struct *curr)
{
        struct trace_array **ptr = private;
        struct trace_array *tr = *ptr;
        struct trace_array_cpu *data;
        unsigned long flags;
        long disabled;
        int cpu;

        if (!tracer_enabled)
                return;

        tracing_record_cmdline(curr);

        local_irq_save(flags);
        cpu = raw_smp_processor_id();
        data = tr->data[cpu];
        disabled = atomic_inc_return(&data->disabled);

        if (likely(disabled == 1))
                tracing_sched_wakeup_trace(tr, data, wakee, curr, flags);

        atomic_dec(&data->disabled);
        local_irq_restore(flags);
}

static notrace void
wake_up_callback(void *probe_data, void *call_data,
                 const char *format, va_list *args)
{
        struct task_struct *curr;
        struct task_struct *task;
        struct rq *__rq;

        if (likely(!tracer_enabled))
                return;

        /* Skip pid %d state %ld */
        (void)va_arg(*args, int);
        (void)va_arg(*args, long);
        /* now get the meat: "rq %p task %p rq->curr %p" */
        __rq = va_arg(*args, typeof(__rq));
        task = va_arg(*args, typeof(task));
        curr = va_arg(*args, typeof(curr));

        tracing_record_cmdline(task);
        tracing_record_cmdline(curr);

        wakeup_func(probe_data, __rq, task, curr);
}

static void sched_switch_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 int tracing_sched_register(void)
{
        int ret;

        ret = marker_probe_register("kernel_sched_wakeup",
                        "pid %d state %ld ## rq %p task %p rq->curr %p",
                        wake_up_callback,
                        &ctx_trace);
        if (ret) {
                pr_info("wakeup trace: Couldn't add marker"
                        " probe to kernel_sched_wakeup\n");
                return ret;
        }

        ret = marker_probe_register("kernel_sched_wakeup_new",
                        "pid %d state %ld ## rq %p task %p rq->curr %p",
                        wake_up_callback,
                        &ctx_trace);
        if (ret) {
                pr_info("wakeup trace: Couldn't add marker"
                        " probe to kernel_sched_wakeup_new\n");
                goto fail_deprobe;
        }

        ret = marker_probe_register("kernel_sched_schedule",
                "prev_pid %d next_pid %d prev_state %ld "
                "## rq %p prev %p next %p",
                sched_switch_callback,
                &ctx_trace);
        if (ret) {
                pr_info("sched trace: Couldn't add marker"
                        " probe to kernel_sched_schedule\n");
                goto fail_deprobe_wake_new;
        }

        return ret;
fail_deprobe_wake_new:
        marker_probe_unregister("kernel_sched_wakeup_new",
                                wake_up_callback,
                                &ctx_trace);
fail_deprobe:
        marker_probe_unregister("kernel_sched_wakeup",
                                wake_up_callback,
                                &ctx_trace);
        return ret;
}

static void tracing_sched_unregister(void)
{
        marker_probe_unregister("kernel_sched_schedule",
                                sched_switch_callback,
                                &ctx_trace);
        marker_probe_unregister("kernel_sched_wakeup_new",
                                wake_up_callback,
                                &ctx_trace);
        marker_probe_unregister("kernel_sched_wakeup",
                                wake_up_callback,
                                &ctx_trace);
}

static void tracing_start_sched_switch(void)
{
        long ref;

        ref = atomic_inc_return(&sched_ref);
        if (ref == 1)
                tracing_sched_register();
}

static void tracing_stop_sched_switch(void)
{
        long ref;

        ref = atomic_dec_and_test(&sched_ref);
        if (ref)
                tracing_sched_unregister();
}

void tracing_start_cmdline_record(void)
{
        tracing_start_sched_switch();
}

void tracing_stop_cmdline_record(void)
{
        tracing_stop_sched_switch();
}

static void start_sched_trace(struct trace_array *tr)
{
        sched_switch_reset(tr);
        tracing_start_cmdline_record();
        tracer_enabled = 1;
}

static void stop_sched_trace(struct trace_array *tr)
{
        tracer_enabled = 0;
        tracing_stop_cmdline_record();
}

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

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

static void sched_switch_trace_reset(struct trace_array *tr)
{
        if (tr->ctrl)
                stop_sched_trace(tr);
}

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

static struct tracer sched_switch_trace __read_mostly =
{
        .name           = "sched_switch",
        .init           = sched_switch_trace_init,
        .reset          = sched_switch_trace_reset,
        .ctrl_update    = sched_switch_trace_ctrl_update,
#ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_sched_switch,
#endif
};

__init static int init_sched_switch_trace(void)
{
        int ret = 0;

        if (atomic_read(&sched_ref))
                ret = tracing_sched_register();
        if (ret) {
                pr_info("error registering scheduler trace\n");
                return ret;
        }
        return register_tracer(&sched_switch_trace);
}
device_initcall(init_sched_switch_trace);