trace_sched_wakeup.c

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/*
 * trace task wakeup timings
 *
 * Copyright (C) 2007-2008 Steven Rostedt <[email protected]>
 * Copyright (C) 2008 Ingo Molnar <[email protected]>
 *
 * 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 void __wakeup_reset(struct trace_array *tr);
static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
static void wakeup_graph_return(struct ftrace_graph_ret *trace);

static int save_lat_flag;

#define TRACE_DISPLAY_GRAPH     1

static struct tracer_opt trace_opts[] = {
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
    /* display latency trace as call graph */
    { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
#endif
    { } /* Empty entry */
};

static struct tracer_flags tracer_flags = {
    .val  = 0,
    .opts = trace_opts,
};

#define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)

#ifdef CONFIG_FUNCTION_TRACER

/*
 * Prologue for the wakeup function tracers.
 *
 * Returns 1 if it is OK to continue, and preemption
 *            is disabled and data->disabled is incremented.
 *         0 if the trace is to be ignored, and preemption
 *            is not disabled and data->disabled is
 *            kept the same.
 *
 * Note, this function is also used outside this ifdef but
 *  inside the #ifdef of the function graph tracer below.
 *  This is OK, since the function graph tracer is
 *  dependent on the function tracer.
 */
static int
func_prolog_preempt_disable(struct trace_array *tr,
                struct trace_array_cpu **data,
                int *pc)
{
    long disabled;
    int cpu;

    if (likely(!wakeup_task))
        return 0;

    *pc = preempt_count();
    preempt_disable_notrace();

    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;

    return 1;

out:
    atomic_dec(&(*data)->disabled);

out_enable:
    preempt_enable_notrace();
    return 0;
}

/*
 * wakeup uses its own tracer function to keep the overhead down:
 */
static void
wakeup_tracer_call(unsigned long ip, unsigned long parent_ip,
           struct ftrace_ops *op, struct pt_regs *pt_regs)
{
    struct trace_array *tr = wakeup_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    int pc;

    if (!func_prolog_preempt_disable(tr, &data, &pc))
        return;

    local_irq_save(flags);
    trace_function(tr, ip, parent_ip, flags, pc);
    local_irq_restore(flags);

    atomic_dec(&data->disabled);
    preempt_enable_notrace();
}

static struct ftrace_ops trace_ops __read_mostly =
{
    .func = wakeup_tracer_call,
    .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE,
};
#endif /* CONFIG_FUNCTION_TRACER */

static int start_func_tracer(int graph)
{
    int ret;

    if (!graph)
        ret = register_ftrace_function(&trace_ops);
    else
        ret = register_ftrace_graph(&wakeup_graph_return,
                        &wakeup_graph_entry);

    if (!ret && tracing_is_enabled())
        tracer_enabled = 1;
    else
        tracer_enabled = 0;

    return ret;
}

static void stop_func_tracer(int graph)
{
    tracer_enabled = 0;

    if (!graph)
        unregister_ftrace_function(&trace_ops);
    else
        unregister_ftrace_graph();
}

#ifdef CONFIG_FUNCTION_GRAPH_TRACER
static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
{

    if (!(bit & TRACE_DISPLAY_GRAPH))
        return -EINVAL;

    if (!(is_graph() ^ set))
        return 0;

    stop_func_tracer(!set);

    wakeup_reset(wakeup_trace);
    tracing_max_latency = 0;

    return start_func_tracer(set);
}

static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
    struct trace_array *tr = wakeup_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    int pc, ret = 0;

    if (!func_prolog_preempt_disable(tr, &data, &pc))
        return 0;

    local_save_flags(flags);
    ret = __trace_graph_entry(tr, trace, flags, pc);
    atomic_dec(&data->disabled);
    preempt_enable_notrace();

    return ret;
}

static void wakeup_graph_return(struct ftrace_graph_ret *trace)
{
    struct trace_array *tr = wakeup_trace;
    struct trace_array_cpu *data;
    unsigned long flags;
    int pc;

    if (!func_prolog_preempt_disable(tr, &data, &pc))
        return;

    local_save_flags(flags);
    __trace_graph_return(tr, trace, flags, pc);
    atomic_dec(&data->disabled);

    preempt_enable_notrace();
    return;
}

static void wakeup_trace_open(struct trace_iterator *iter)
{
    if (is_graph())
        graph_trace_open(iter);
}

static void wakeup_trace_close(struct trace_iterator *iter)
{
    if (iter->private)
        graph_trace_close(iter);
}

#define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \
                TRACE_GRAPH_PRINT_ABS_TIME | \
                TRACE_GRAPH_PRINT_DURATION)

static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
    /*
     * In graph mode call the graph tracer output function,
     * otherwise go with the TRACE_FN event handler
     */
    if (is_graph())
        return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);

    return TRACE_TYPE_UNHANDLED;
}

static void wakeup_print_header(struct seq_file *s)
{
    if (is_graph())
        print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
    else
        trace_default_header(s);
}

static void
__trace_function(struct trace_array *tr,
         unsigned long ip, unsigned long parent_ip,
         unsigned long flags, int pc)
{
    if (is_graph())
        trace_graph_function(tr, ip, parent_ip, flags, pc);
    else
        trace_function(tr, ip, parent_ip, flags, pc);
}
#else
#define __trace_function trace_function

static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
{
    return -EINVAL;
}

static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
{
    return -1;
}

static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
{
    return TRACE_TYPE_UNHANDLED;
}

static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
static void wakeup_trace_open(struct trace_iterator *iter) { }
static void wakeup_trace_close(struct trace_iterator *iter) { }

#ifdef CONFIG_FUNCTION_TRACER
static void wakeup_print_header(struct seq_file *s)
{
    trace_default_header(s);
}
#else
static void wakeup_print_header(struct seq_file *s)
{
    trace_latency_header(s);
}
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* CONFIG_FUNCTION_GRAPH_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();

    if (start_func_tracer(is_graph()))
        printk(KERN_ERR "failed to start wakeup tracer\n");

    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;
    stop_func_tracer(is_graph());
    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,
    .print_header   = wakeup_print_header,
    .print_line = wakeup_print_line,
    .flags      = &tracer_flags,
    .set_flag   = wakeup_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest    = trace_selftest_startup_wakeup,
#endif
    .open       = wakeup_trace_open,
    .close      = wakeup_trace_close,
    .use_max_tr = 1,
};

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,
    .print_header   = wakeup_print_header,
    .print_line = wakeup_print_line,
    .flags      = &tracer_flags,
    .set_flag   = wakeup_set_flag,
#ifdef CONFIG_FTRACE_SELFTEST
    .selftest    = trace_selftest_startup_wakeup,
#endif
    .open       = wakeup_trace_open,
    .close      = wakeup_trace_close,
    .use_max_tr = 1,
};

__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);