linux-kernel - [PATCH] sched/fair: Update rq clock before updating nohz cpu load

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Message-Id: <1462304814-11715-1-git-send-email-matt@codeblueprint.co.uk>
Date:	Tue,  3 May 2016 20:46:54 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>
Subject: [PATCH] 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().

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Mike Galbraith <umgwanakikbuti@...il.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Rik van Riel <riel@...hat.com>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 kernel/sched/fair.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b8a33abce650..aa9ba82f0d7c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4723,6 +4723,7 @@ 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);
 }
-- 
2.7.3