linux-kernel - Re: sched: Reenable interrupts in do sched

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Date:   Tue, 20 Oct 2020 11:38:30 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: sched: Reenable interrupts in do sched_yield()

On Tue, 20 Oct 2020 16:46:55 +0200
Thomas Gleixner <tglx@...utronix.de> wrote:

> -	/*
> -	 * Since we are going to call schedule() anyway, there's
> -	 * no need to preempt or enable interrupts:

I think the above comment still makes sense, just needs to be tweeked:

	/*
	 * Since we are going to call schedule() anyway, there's
	 * no need to allow preemption after releasing the rq lock.
> -	 */

Especially, since we are now enabling interrupts, which is likely to
trigger a preemption.

-- Steve

>  	preempt_disable();
> -	rq_unlock(rq, &rf);
> +	rq_unlock_irq(rq, &rf);
>  	sched_preempt_enable_no_resched();
>  
>  	schedule();