ftrace: add function tracing to wake up tracing

This patch adds function tracing to the functions that are called
on the CPU of the task being traced.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: pq@iki.fi
Cc: proski@gnu.org
Cc: sandmann@redhat.com
Cc: a.p.zijlstra@chello.nl
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 5d2fb48e47f8194576a5bf87c9fc0600242f89a9..bf7e91caef57d0ae6496688e82530598eab09421 100644 (file)
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -30,6 +30,69 @@ 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?
  */
@@ -73,7 +136,7 @@ wakeup_sched_switch(void *private, void *rq, struct task_struct *prev,
        if (next != wakeup_task)
                return;
 
-       /* The task we are waitng for is waking up */
+       /* The task we are waiting for is waking up */
        data = tr->data[wakeup_cpu];
 
        /* disable local data, not wakeup_cpu data */
@@ -290,6 +353,7 @@ static void start_wakeup_tracer(struct trace_array *tr)
        smp_wmb();
 
        tracer_enabled = 1;
+       register_ftrace_function(&trace_ops);
 
        return;
 fail_deprobe_wake_new:
@@ -305,6 +369,7 @@ fail_deprobe:
 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);