1 files changed, 448 insertions, 0 deletions

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
new file mode 100644
index 000000000000..3c8d61df4474
--- /dev/null
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -0,0 +1,448 @@
+/*
+ * 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 <linux/marker.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 unsigned                 wakeup_prio = -1;
+
+static DEFINE_SPINLOCK(wakeup_lock);
+
+static void __wakeup_reset(struct trace_array *tr);
+
+#ifdef CONFIG_FTRACE
+/*
+ * 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;
+
+        if (likely(!wakeup_task))
+                return;
+
+        resched = need_resched();
+        preempt_disable_notrace();
+
+        cpu = raw_smp_processor_id();
+        data = tr->data[cpu];
+        disabled = atomic_inc_return(&data->disabled);
+        if (unlikely(disabled != 1))
+                goto out;
+
+        spin_lock_irqsave(&wakeup_lock, flags);
+
+        if (unlikely(!wakeup_task))
+                goto unlock;
+
+        /*
+         * The task can't disappear because it needs to
+         * wake up first, and we have the wakeup_lock.
+         */
+        if (task_cpu(wakeup_task) != cpu)
+                goto unlock;
+
+        trace_function(tr, data, ip, parent_ip, flags);
+
+ unlock:
+        spin_unlock_irqrestore(&wakeup_lock, flags);
+
+ out:
+        atomic_dec(&data->disabled);
+
+        /*
+         * To prevent recursion from the scheduler, if the
+         * resched flag was set before we entered, then
+         * don't reschedule.
+         */
+        if (resched)
+                preempt_enable_no_resched_notrace();
+        else
+                preempt_enable_notrace();
+}
+
+static struct ftrace_ops trace_ops __read_mostly =
+{
+        .func = wakeup_tracer_call,
+};
+#endif /* CONFIG_FTRACE */
+
+/*
+ * 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 notrace
+wakeup_sched_switch(void *private, void *rq, struct task_struct *prev,
+        struct task_struct *next)
+{
+        unsigned long latency = 0, t0 = 0, t1 = 0;
+        struct trace_array **ptr = private;
+        struct trace_array *tr = *ptr;
+        struct trace_array_cpu *data;
+        cycle_t T0, T1, delta;
+        unsigned long flags;
+        long disabled;
+        int cpu;
+
+        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;
+
+        /* The task we are waiting for is waking up */
+        data = tr->data[wakeup_cpu];
+
+        /* disable local data, not wakeup_cpu data */
+        cpu = raw_smp_processor_id();
+        disabled = atomic_inc_return(&tr->data[cpu]->disabled);
+        if (likely(disabled != 1))
+                goto out;
+
+        spin_lock_irqsave(&wakeup_lock, flags);
+
+        /* We could race with grabbing wakeup_lock */
+        if (unlikely(!tracer_enabled || next != wakeup_task))
+                goto out_unlock;
+
+        trace_function(tr, data, CALLER_ADDR1, CALLER_ADDR2, flags);
+
+        /*
+         * usecs conversion is slow so we try to delay the conversion
+         * as long as possible:
+         */
+        T0 = data->preempt_timestamp;
+        T1 = ftrace_now(cpu);
+        delta = T1-T0;
+
+        if (!report_latency(delta))
+                goto out_unlock;
+
+        latency = nsecs_to_usecs(delta);
+
+        tracing_max_latency = delta;
+        t0 = nsecs_to_usecs(T0);
+        t1 = nsecs_to_usecs(T1);
+
+        update_max_tr(tr, wakeup_task, wakeup_cpu);
+
+out_unlock:
+        __wakeup_reset(tr);
+        spin_unlock_irqrestore(&wakeup_lock, flags);
+out:
+        atomic_dec(&tr->data[cpu]->disabled);
+}
+
+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;
+
+        /* 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));
+
+        tracing_record_cmdline(prev);
+
+        /*
+         * If tracer_switch_func only points to the local
+         * switch func, it still needs the ptr passed to it.
+         */
+        wakeup_sched_switch(probe_data, __rq, prev, next);
+}
+
+static void __wakeup_reset(struct trace_array *tr)
+{
+        struct trace_array_cpu *data;
+        int cpu;
+
+        assert_spin_locked(&wakeup_lock);
+
+        for_each_possible_cpu(cpu) {
+                data = tr->data[cpu];
+                tracing_reset(data);
+        }
+
+        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;
+
+        spin_lock_irqsave(&wakeup_lock, flags);
+        __wakeup_reset(tr);
+        spin_unlock_irqrestore(&wakeup_lock, flags);
+}
+
+static void
+wakeup_check_start(struct trace_array *tr, struct task_struct *p,
+                   struct task_struct *curr)
+{
+        int cpu = smp_processor_id();
+        unsigned long flags;
+        long disabled;
+
+        if (likely(!rt_task(p)) ||
+                        p->prio >= wakeup_prio ||
+                        p->prio >= curr->prio)
+                return;
+
+        disabled = atomic_inc_return(&tr->data[cpu]->disabled);
+        if (unlikely(disabled != 1))
+                goto out;
+
+        /* interrupts should be off from try_to_wake_up */
+        spin_lock(&wakeup_lock);
+
+        /* check for races. */
+        if (!tracer_enabled || p->prio >= wakeup_prio)
+                goto out_locked;
+
+        /* reset the trace */
+        __wakeup_reset(tr);
+
+        wakeup_cpu = task_cpu(p);
+        wakeup_prio = p->prio;
+
+        wakeup_task = p;
+        get_task_struct(wakeup_task);
+
+        local_save_flags(flags);
+
+        tr->data[wakeup_cpu]->preempt_timestamp = ftrace_now(cpu);
+        trace_function(tr, tr->data[wakeup_cpu],
+                       CALLER_ADDR1, CALLER_ADDR2, flags);
+
+out_locked:
+        spin_unlock(&wakeup_lock);
+out:
+        atomic_dec(&tr->data[cpu]->disabled);
+}
+
+static notrace void
+wake_up_callback(void *probe_data, void *call_data,
+                 const char *format, va_list *args)
+{
+        struct trace_array **ptr = probe_data;
+        struct trace_array *tr = *ptr;
+        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_check_start(tr, task, curr);
+}
+
+static void start_wakeup_tracer(struct trace_array *tr)
+{
+        int ret;
+
+        ret = marker_probe_register("kernel_sched_wakeup",
+                        "pid %d state %ld ## rq %p task %p rq->curr %p",
+                        wake_up_callback,
+                        &wakeup_trace);
+        if (ret) {
+                pr_info("wakeup trace: Couldn't add marker"
+                        " probe to kernel_sched_wakeup\n");
+                return;
+        }
+
+        ret = marker_probe_register("kernel_sched_wakeup_new",
+                        "pid %d state %ld ## rq %p task %p rq->curr %p",
+                        wake_up_callback,
+                        &wakeup_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,
+                &wakeup_trace);
+        if (ret) {
+                pr_info("sched trace: Couldn't add marker"
+                        " probe to kernel_sched_schedule\n");
+                goto fail_deprobe_wake_new;
+        }
+
+        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);
+
+        tracer_enabled = 1;
+
+        return;
+fail_deprobe_wake_new:
+        marker_probe_unregister("kernel_sched_wakeup_new",
+                                wake_up_callback,
+                                &wakeup_trace);
+fail_deprobe:
+        marker_probe_unregister("kernel_sched_wakeup",
+                                wake_up_callback,
+                                &wakeup_trace);
+}
+
+static void stop_wakeup_tracer(struct trace_array *tr)
+{
+        tracer_enabled = 0;
+        unregister_ftrace_function(&trace_ops);
+        marker_probe_unregister("kernel_sched_schedule",
+                                sched_switch_callback,
+                                &wakeup_trace);
+        marker_probe_unregister("kernel_sched_wakeup_new",
+                                wake_up_callback,
+                                &wakeup_trace);
+        marker_probe_unregister("kernel_sched_wakeup",
+                                wake_up_callback,
+                                &wakeup_trace);
+}
+
+static void wakeup_tracer_init(struct trace_array *tr)
+{
+        wakeup_trace = tr;
+
+        if (tr->ctrl)
+                start_wakeup_tracer(tr);
+}
+
+static void wakeup_tracer_reset(struct trace_array *tr)
+{
+        if (tr->ctrl) {
+                stop_wakeup_tracer(tr);
+                /* make sure we put back any tasks we are tracing */
+                wakeup_reset(tr);
+        }
+}
+
+static void wakeup_tracer_ctrl_update(struct trace_array *tr)
+{
+        if (tr->ctrl)
+                start_wakeup_tracer(tr);
+        else
+                stop_wakeup_tracer(tr);
+}
+
+static void wakeup_tracer_open(struct trace_iterator *iter)
+{
+        /* stop the trace while dumping */
+        if (iter->tr->ctrl)
+                stop_wakeup_tracer(iter->tr);
+}
+
+static void wakeup_tracer_close(struct trace_iterator *iter)
+{
+        /* forget about any processes we were recording */
+        if (iter->tr->ctrl)
+                start_wakeup_tracer(iter->tr);
+}
+
+static struct tracer wakeup_tracer __read_mostly =
+{
+        .name           = "wakeup",
+        .init           = wakeup_tracer_init,
+        .reset          = wakeup_tracer_reset,
+        .open           = wakeup_tracer_open,
+        .close          = wakeup_tracer_close,
+        .ctrl_update    = wakeup_tracer_ctrl_update,
+        .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;
+
+        return 0;
+}
+device_initcall(init_wakeup_tracer);