linux-kernel - Re: [RFC] Repeated rto_push_irq_work

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Message-ID: <20241002103749.14d713c1@gandalf.local.home>
Date: Wed, 2 Oct 2024 10:37:49 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev, Ben Segall
 <bsegall@...gle.com>, Dietmar Eggemann <dietmar.eggemann@....com>, Ingo
 Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Mel Gorman
 <mgorman@...e.de>, Peter Zijlstra <peterz@...radead.org>, Valentin
 Schneider <vschneid@...hat.com>, Vincent Guittot
 <vincent.guittot@...aro.org>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] Repeated rto_push_irq_work_func() invocation.

On Wed, 2 Oct 2024 13:21:05 +0200
Sebastian Andrzej Siewior <bigeasy@...utronix.de> wrote:

> Would it make sense to avoid scheduling rto_push_work if rq->curr has
> NEED_RESCHED set and make the scheduler do push_rt_task()?

Can we safely check rq->curr without taking any locks on that CPU?

I guess tasks do not get freed while a CPU has preemption disabled, so it
may be safe to do:

	task = READ_ONCE(rq->curr);
	if (test_task_need_resched(task))
		/* skip */

??

-- Steve