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Message-ID: <20211202210221.GB16608@worktop.programming.kicks-ass.net>
Date: Thu, 2 Dec 2021 22:02:21 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, Ben Segall <bsegall@...gle.com>,
Boqun Feng <boqun.feng@...il.com>,
Daniel Bristot de Oliveira <bristot@...hat.com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Ingo Molnar <mingo@...hat.com>,
Juri Lelli <juri.lelli@...hat.com>,
Mel Gorman <mgorman@...e.de>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>,
Vincent Guittot <vincent.guittot@...aro.org>,
Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH 01/11] sched: Trigger warning if ->migration_disabled
counter underflows.
On Mon, Nov 29, 2021 at 06:46:44PM +0100, Sebastian Andrzej Siewior wrote:
> If migrate_enable() is used more often than its counter part then it
> remains undetected and rq::nr_pinned will underflow, too.
>
> Add a warning if migrate_enable() is attempted if without a matching a
> migrate_disable().
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
> kernel/sched/core.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 76f9deeaa9420..02be3f6144e97 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2171,6 +2171,8 @@ void migrate_enable(void)
> if (p->migration_disabled > 1) {
> p->migration_disabled--;
> return;
Due to return there ^
> + } else if (WARN_ON_ONCE(p->migration_disabled == 0)) {
> + return;
> }
we can do away with else and simply write:
if (WARN_ON_ONCE(!p->migration_disabled))
return;
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