[tip:sched/core] sched: Update rq clock before calling check_preempt_curr()

[tip-bot for Frederic Weisbecker]

Commit-ID:  1ad4ec0dc740c4183acd6d6e367ca52b28e4fa94
Gitweb:     http://git.kernel.org/tip/1ad4ec0dc740c4183acd6d6e367ca52b28e4fa94
Author:     Frederic Weisbecker <fweisbec@xxxxxxxxx>
AuthorDate: Fri, 12 Apr 2013 01:51:00 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 28 May 2013 09:40:24 +0200

sched: Update rq clock before calling check_preempt_curr()

check_preempt_curr() of fair class needs an uptodate sched clock
value to update runtime stats of the current task of the target's rq.

When a task is woken up, activate_task() is usually called right before
ttwu_do_wakeup() unless the task is still in the runqueue. In the latter
case we need to update the rq clock explicitly because activate_task()
isn't here to do the job for us.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1365724262-20142-4-git-send-email-fweisbec@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/sched/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7bf0418..46d0017 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1365,6 +1365,8 @@ static int ttwu_remote(struct task_struct *p, int wake_flags)
 
 	rq = __task_rq_lock(p);
 	if (p->on_rq) {
+		/* check_preempt_curr() may use rq clock */
+		update_rq_clock(rq);
 		ttwu_do_wakeup(rq, p, wake_flags);
 		ret = 1;
 	}
--
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