linux-kernel - [RFC][PATCH 3/5] sched/core: Reset RQCF_ACT

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Date:	Thu, 12 May 2016 20:49:51 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Byungchul Park <byungchul.park@....com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Luca Abeni <luca.abeni@...tn.it>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wanpeng Li <wanpeng.li@...mail.com>,
	Yuyang Du <yuyang.du@...el.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Mike Galbraith <umgwanakikbuti@...il.com>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: [RFC][PATCH 3/5] sched/core: Reset RQCF_ACT_SKIP before unpinning rq->lock

rq_clock() is called from sched_info_{depart,arrive}() after resetting
RQCF_ACT_SKIP but prior to a call to update_rq_clock().

In preparation for pending patches that check whether the rq clock has
been updated inside of a pin context before rq_clock() is called, move
the reset of rq->clock_skip_update immediately before unpinning the rq
lock.

This will avoid the new warnings which check if update_rq_clock() is
being actively skipped.

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>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 kernel/sched/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index dfdd8c3c083b..d2112c268fd1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2824,6 +2824,9 @@ context_switch(struct rq *rq, struct task_struct *prev,
 		prev->active_mm = NULL;
 		rq->prev_mm = oldmm;
 	}
+
+	rq->clock_skip_update = 0;
+
 	/*
 	 * Since the runqueue lock will be released by the next
 	 * task (which is an invalid locking op but in the case
@@ -3316,7 +3319,6 @@ static void __sched notrace __schedule(bool preempt)
 	next = pick_next_task(rq, prev, &rf);
 	clear_tsk_need_resched(prev);
 	clear_preempt_need_resched();
-	rq->clock_skip_update = 0;
 
 	if (likely(prev != next)) {
 		rq->nr_switches++;
@@ -3326,6 +3328,7 @@ static void __sched notrace __schedule(bool preempt)
 		trace_sched_switch(preempt, prev, next);
 		rq = context_switch(rq, prev, next, &rf); /* unlocks the rq */
 	} else {
+		rq->clock_skip_update = 0;
 		rq_unpin_lock(rq, &rf);
 		raw_spin_unlock_irq(&rq->lock);
 	}
-- 
2.7.3