linux-kernel - Re: [PATCH] sched: optimize __cond_resched

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Message-ID: <YcGVzClid/7q3DuB@hirez.programming.kicks-ass.net>
Date:   Tue, 21 Dec 2021 09:52:28 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     xuhaifeng <xuhaifeng@...o.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: optimize __cond_resched_lock()

On Tue, Dec 21, 2021 at 03:23:16PM +0800, xuhaifeng wrote:
> if the kernel is preemptible(CONFIG_PREEMPTION=y), schedule()may be
> called twice, once via spin_unlock, once via preempt_schedule_common.
> 
> we can add one conditional, check TIF_NEED_RESCHED flag again,
> to avoid this.

You can also make it more similar to __cond_resched() instead of making
it more different.