linux-kernel - [PATCH 1/5] sched: Update rq clock before migrating tasks out of dying CPU

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Date:	Fri, 12 Apr 2013 01:50:58 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>, Mike Galbraith <efault@....de>
Subject: [PATCH 1/5] sched: Update rq clock before migrating tasks out of dying CPU

Because the sched_class::put_prev_task() callback of rt and fair
classes are referring to the rq clock to update their runtime
statistics. There is a missing rq clock update from the CPU
hotplug notifier's entrypoint of the scheduler.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Li Zhong <zhong@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Paul Turner <pjt@...gle.com>
Cc: Mike Galbraith <efault@....de>
---
 kernel/sched/core.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee8c1bd..ec036d8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4928,6 +4928,13 @@ static void migrate_tasks(unsigned int dead_cpu)
 	 */
 	rq->stop = NULL;
 
+	/*
+	 * put_prev_task() and pick_next_task() sched
+	 * class method both need to have an up-to-date
+	 * value of rq->clock[_task]
+	 */
+	update_rq_clock(rq);
+
 	for ( ; ; ) {
 		/*
 		 * There's this thread running, bail when that's the only
-- 
1.7.5.4

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