/*
 * 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 raw_spinlock_t wakeup_lock =
        (raw_spinlock_t)__RAW_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);
        __raw_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);
        __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)
{
        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);
        __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 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 */
        __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_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:
        __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_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);