linux-kernel - [tip:sched/core] sched/tracing: Allow tracing the preemption decision on wakeup

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Message-ID: <tip-a8d7ad52a7befbde896276d05c75c90fed48b5bf@git.kernel.org>
Date:	Mon, 18 Mar 2013 04:09:05 -0700
From:	tip-bot for Peter Zijlstra <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	a.p.zijlstra@...llo.nl, efault@....de, pjt@...gle.com,
	peterz@...radead.org, rostedt@...dmis.org, tglx@...utronix.de
Subject: [tip:sched/core] sched/tracing:
  Allow tracing the preemption decision on wakeup

Commit-ID:  a8d7ad52a7befbde896276d05c75c90fed48b5bf
Gitweb:     http://git.kernel.org/tip/a8d7ad52a7befbde896276d05c75c90fed48b5bf
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Thu, 14 Mar 2013 10:48:39 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 18 Mar 2013 10:18:08 +0100

sched/tracing: Allow tracing the preemption decision on wakeup

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@...utronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Acked-by: Steven Rostedt <rostedt@...dmis.org>
Acked-by: Paul Turner <pjt@...gle.com>
Cc: Mike Galbraith <efault@....de>
Link: http://lkml.kernel.org/r/1363254519.26965.9.camel@laptop
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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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