[PATCH] sched,trace: Allow tracing the preemption decision on wakeup

[Peter Zijlstra]

Thomas noted that we do the wakeup preemption check after the wakeup
trace point, this means the tracepoint cannot test/report this decision;
which is rather important for latency sensitive workloads. Therefore
move the tracepoint after doing the preemption check.

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b36635e..849deb9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1288,8 +1288,8 @@ static void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
 static void
 ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
 {
-	trace_sched_wakeup(p, true);
 	check_preempt_curr(rq, p, wake_flags);
+	trace_sched_wakeup(p, true);
 
 	p->state = TASK_RUNNING;
 #ifdef CONFIG_SMP


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