linux-kernel - Re: [PATCH 1/8] sched: Fix hrtick() vs scheduling context

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Message-ID: <CANDhNCr3hAsJRSMx9-yHA6Jv6ASCgjqGH=vVO4JhRSTp2v+0xg@mail.gmail.com>
Date: Mon, 22 Sep 2025 17:24:01 -0700
From: John Stultz <jstultz@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: tglx@...utronix.de, arnd@...db.de, anna-maria@...utronix.de, 
	frederic@...nel.org, luto@...nel.org, mingo@...hat.com, juri.lelli@...hat.com, 
	vincent.guittot@...aro.org, dietmar.eggemann@....com, rostedt@...dmis.org, 
	bsegall@...gle.com, mgorman@...e.de, vschneid@...hat.com, 
	linux-kernel@...r.kernel.org, oliver.sang@...el.com
Subject: Re: [PATCH 1/8] sched: Fix hrtick() vs scheduling context

On Thu, Sep 18, 2025 at 1:06 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> The sched_class::task_tick() method is called on the donor
> sched_class, and sched_tick() hands it rq->donor as argument, which is
> consistent.
>
> However, while hrtick() uses the donor sched_class, it then passes
> rq->curr, which is inconsistent. Fix it.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> ---
>  kernel/sched/core.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -875,7 +875,7 @@ static enum hrtimer_restart hrtick(struc
>
>         rq_lock(rq, &rf);
>         update_rq_clock(rq);
> -       rq->donor->sched_class->task_tick(rq, rq->curr, 1);
> +       rq->donor->sched_class->task_tick(rq, rq->donor, 1);
>         rq_unlock(rq, &rf);

Ah. Thanks for catching this! I've run through with some stress
testing on this and haven't seen any problems so far.

Acked-by: John Stultz <jstultz@...gle.com>

thanks
-john