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From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Ingo Molnar <mingo@kernel.org>,
	Mel Gorman <mgorman@suse.de>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>
Subject: Re: [PATCH V2] sched: Prevent balance_push() on remote runqueues
Date: Mon, 30 Aug 2021 11:12:12 +0200	[thread overview]
Message-ID: <20210830091212.GG4353@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <87zgt1hdw7.ffs@tglx>

On Sat, Aug 28, 2021 at 03:55:52PM +0200, Thomas Gleixner wrote:
> sched_setscheduler() and rt_mutex_setprio() invoke the run-queue balance
> callback after changing priorities or the scheduling class of a task. The
> run-queue for which the callback is invoked can be local or remote.
> 
> That's not a problem for the regular rq::push_work which is serialized with
> a busy flag in the run-queue struct, but for the balance_push() work which
> is only valid to be invoked on the outgoing CPU that's wrong. It not only
> triggers the debug warning, but also leaves the per CPU variable push_work
> unprotected, which can result in double enqueues on the stop machine list.
> 
> Remove the warning and validate that the function is invoked on the
> outgoing CPU.
> 
> Fixes: ae7927023243 ("sched: Optimize finish_lock_switch()")
> Reported-by: Sebastian Siewior <bigeasy@linutronix.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Thanks!

  parent reply	other threads:[~2021-08-30  9:13 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 14:07 [PATCH] sched: Prevent balance_push() on remote runqueues Thomas Gleixner
2021-08-28  7:21 ` Thomas Gleixner
2021-08-28 13:55   ` [PATCH V2] " Thomas Gleixner
2021-08-28 17:17     ` Tao Zhou
2021-08-30  9:12     ` Peter Zijlstra [this message]
2021-09-09  9:38     ` [tip: sched/urgent] " tip-bot2 for Thomas Gleixner

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