[PATCH] sched: deliver sched_switch events to a current task

[Andrew Vagin]

Otherwise they can't be filtered for a defined task.

perf record -e sched:sched_switch ./foo

This command doesn't report any event without this patch.

I think it isn't a big problem for security, if someone will know
who will be executed next. By default perf is disabled for non-root
users.

I need this events for profiling sleep times.  sched_switch is used for
getting callchains and sched_stat_* is used for getting time periods.
This events are combined in user space, then it can be analized by
perf tools.

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Arun Sharma <asharma@xxxxxx>
Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx>
---
 kernel/sched/core.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d5594a4..c5d6a0f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1910,12 +1910,12 @@ static inline void
 prepare_task_switch(struct rq *rq, struct task_struct *prev,
 		    struct task_struct *next)
 {
+	trace_sched_switch(prev, next);
 	sched_info_switch(prev, next);
 	perf_event_task_sched_out(prev, next);
 	fire_sched_out_preempt_notifiers(prev, next);
 	prepare_lock_switch(rq, next);
 	prepare_arch_switch(next);
-	trace_sched_switch(prev, next);
 }
 
 /**
-- 
1.7.1

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