sched: Deliver sched_switch events to the current task

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

  perf record -e sched:sched_switch ./foo

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

I think it isn't a security concern if someone knows who will
be executed next - this can already be observed by polling /proc
state. By default perf is disabled for non-root users in any case.

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

Signed-off-by: Andrew Vagin <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Arun Sharma <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 468bdd44c1baeb914cfc93037b86691b839ccc46..ad732b56ba70665680fdc1e73793f60bab562baa 100644 (file)
--- 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);
 }
 
 /**