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From: Thomas Gleixner <tglx@linutronix.de>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@kernel.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: sched: Reenable interrupts in do sched_yield()
Date: Tue, 20 Oct 2020 20:02:55 +0200	[thread overview]
Message-ID: <87o8kw93n4.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201020113830.378b4a4c@gandalf.local.home>

On Tue, Oct 20 2020 at 11:38, Steven Rostedt wrote:
> On Tue, 20 Oct 2020 16:46:55 +0200
> Thomas Gleixner <tglx@linutronix.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.

sched_preempt_enable_no_resched() still enables preemption. It just
avoids the check. And it still allows preemption when an interrupt
triggering preemption happens between sched_preempt_enable_no_resched()
and __schedule() disabling preemption/interrupts.

So no, your new variant is just differently bogus and misleading.

Thanks,

        tglx

  reply	other threads:[~2020-10-20 18:03 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-20 14:46 Thomas Gleixner
2020-10-20 15:38 ` Steven Rostedt
2020-10-20 18:02   ` Thomas Gleixner [this message]
2020-10-20 20:07     ` Steven Rostedt
2020-10-21  7:27       ` Thomas Gleixner
2020-10-21 14:07         ` Steven Rostedt
2020-12-23 12:02           ` Qais Yousef
2020-10-29 10:51 ` [tip: sched/core] sched: Reenable interrupts in do_sched_yield() tip-bot2 for Thomas Gleixner

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