linux-kernel - [tip:sched/core] sched/fair: Update rq clock before updating nohz CPU load

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Date:	Thu, 5 May 2016 02:42:09 -0700
From:	tip-bot for Matt Fleming <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	matt@...eblueprint.co.uk, torvalds@...ux-foundation.org,
	mingo@...nel.org, riel@...hat.com, mgorman@...hsingularity.net,
	efault@....de, peterz@...radead.org, hpa@...or.com,
	umgwanakikbuti@...il.com, wanpeng.li@...mail.com,
	linux-kernel@...r.kernel.org, fweisbec@...il.com,
	tglx@...utronix.de
Subject: [tip:sched/core] sched/fair: Update rq clock before updating nohz
 CPU load

Commit-ID:  b52fad2db5d792d89975cebf2fe1646a7af28ed0
Gitweb:     http://git.kernel.org/tip/b52fad2db5d792d89975cebf2fe1646a7af28ed0
Author:     Matt Fleming <matt@...eblueprint.co.uk>
AuthorDate: Tue, 3 May 2016 20:46:54 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 5 May 2016 09:41:09 +0200

sched/fair: Update rq clock before updating nohz CPU load

If we're accessing rq_clock() (e.g. in sched_avg_update()) we should
update the rq clock before calling cpu_load_update(), otherwise any
time calculations will be stale.

All other paths currently call update_rq_clock().

Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Wanpeng Li <wanpeng.li@...mail.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Mike Galbraith <efault@....de>
Cc: Mike Galbraith <umgwanakikbuti@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Rik van Riel <riel@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1462304814-11715-1-git-send-email-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8c381a6..7a00c7c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4724,6 +4724,7 @@ void cpu_load_update_nohz_stop(void)
 
 	load = weighted_cpuload(cpu_of(this_rq));
 	raw_spin_lock(&this_rq->lock);
+	update_rq_clock(this_rq);
 	cpu_load_update_nohz(this_rq, curr_jiffies, load);
 	raw_spin_unlock(&this_rq->lock);
 }