Commit 457be908 authored Apr 26, 2018 by Vincent Guittot Committed by Ingo Molnar May 03, 2018

sched/fair: Fix the update of blocked load when newly idle



With commit:

  31e77c93 ("sched/fair: Update blocked load when newly idle")

... we release the rq->lock when updating blocked load of idle CPUs.

This opens a time window during which another CPU can add a task to this
CPU's cfs_rq.

The check for newly added task of idle_balance() is not in the common path.
Move the out label to include this check.

Reported-by: Heiner Kallweit <hkallweit1@gmail.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 31e77c93 ("sched/fair: Update blocked load when newly idle")
Link: http://lkml.kernel.org/r/20180426103133.GA6953@linaro.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 0b26351b

kernel/sched/fair.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -9847,6 +9847,7 @@ static int idle_balance(struct rq this_rq, struct rq_flags rf)
		if (curr_cost > this_rq->max_idle_balance_cost)
		this_rq->max_idle_balance_cost = curr_cost;

		out:
		/*
		* While browsing the domains, we released the rq lock, a task could
		* have been enqueued in the meantime. Since we're not going idle,
		@@ -9855,7 +9856,6 @@ static int idle_balance(struct rq this_rq, struct rq_flags rf)
		if (this_rq->cfs.h_nr_running && !pulled_task)
		pulled_task = 1;

		out:
		/* Move the next balance forward */
		if (time_after(this_rq->next_balance, next_balance))
		this_rq->next_balance = next_balance;

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