[02/19] sched: add latency tracer callbacks to the scheduler

[02/19] sched: add latency tracer callbacks to the scheduler

[Ingo Molnar]

From: Ingo Molnar <mingo@elte.hu>

add 3 lightweight callbacks to the tracer backend.

zero impact if tracing is turned off.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 include/linux/sched.h |   26 ++++++++++++++++++++++++++
 kernel/sched.c        |    3 +++
 2 files changed, 29 insertions(+)

Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -2027,6 +2027,32 @@ extern int sched_mc_power_savings, sched
 
 extern void normalize_rt_tasks(void);
 
+#ifdef CONFIG_CONTEXT_SWITCH_TRACER
+extern void
+ftrace_ctx_switch(struct task_struct *prev, struct task_struct *next);
+#else
+static inline void
+ftrace_ctx_switch(struct task_struct *prev, struct task_struct *next)
+{
+}
+#endif
+
+#ifdef CONFIG_SCHED_TRACER
+extern void
+ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr);
+extern void
+ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr);
+#else
+static inline void
+ftrace_wake_up_task(struct task_struct *wakee, struct task_struct *curr)
+{
+}
+static inline void
+ftrace_wake_up_new_task(struct task_struct *wakee, struct task_struct *curr)
+{
+}
+#endif
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 
 extern struct task_group init_task_group;
Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -1867,6 +1867,7 @@ static int try_to_wake_up(struct task_st
 
 out_activate:
 #endif /* CONFIG_SMP */
+	ftrace_wake_up_task(p, rq->curr);
 	schedstat_inc(p, se.nr_wakeups);
 	if (sync)
 		schedstat_inc(p, se.nr_wakeups_sync);
@@ -2007,6 +2008,7 @@ void wake_up_new_task(struct task_struct
 		p->sched_class->task_new(rq, p);
 		inc_nr_running(rq);
 	}
+	ftrace_wake_up_new_task(p, rq->curr);
 	check_preempt_curr(rq, p);
 #ifdef CONFIG_SMP
 	if (p->sched_class->task_wake_up)
@@ -2179,6 +2181,7 @@ context_switch(struct rq *rq, struct tas
 	struct mm_struct *mm, *oldmm;
 
 	prepare_task_switch(rq, prev, next);
+	ftrace_ctx_switch(prev, next);
 	mm = next->mm;
 	oldmm = prev->active_mm;
 	/*