linux-kernel - Re: [PATCH v2] hrtimer: select housekeeping CPU during migration

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Date: Tue, 13 Feb 2024 20:41:30 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Costa Shulyupin <costa.shul@...hat.com>, linux-kernel@...r.kernel.org
Cc: Costa Shulyupin <costa.shul@...hat.com>, Waiman Long
 <longman@...hat.com>, Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH v2] hrtimer: select housekeeping CPU during migration

On Tue, Feb 13 2024 at 18:46, Costa Shulyupin wrote:

Way better now. Two nitpicks though:

> During CPU-down hotplug, hrtimers may migrate to isolated CPUs,
> compromising CPU isolation. This commit addresses this issue by
> masking valid CPUs for hrtimers using housekeeping_cpumask(HK_TYPE_TIMER).

'This commit' is pointless.

 # git grep 'This patch' Documentation/process/

gives you an hint.

> Suggested-by: Waiman Long <longman@...hat.com>
> Signed-off-by: Costa Shulyupin <costa.shul@...hat.com>
> Reviewed-by: Waiman Long <longman@...hat.com>
> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>
> ---
>
> Changes in v2:
> - [v1] https://lore.kernel.org/all/20240211135213.2518068-1-costa.shul@redhat.com/
> - reworded and rebased on linux-next
> ---
>  kernel/time/hrtimer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
> index edb0f821dcea..947bd6cf7105 100644
> --- a/kernel/time/hrtimer.c
> +++ b/kernel/time/hrtimer.c
> @@ -2224,7 +2224,7 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
>  int hrtimers_cpu_dying(unsigned int dying_cpu)
>  {
>  	struct hrtimer_cpu_base *old_base, *new_base;
> -	int i, ncpu = cpumask_first(cpu_active_mask);
> +	int i, ncpu = cpumask_any_and(cpu_active_mask, housekeeping(HK_TYPE_TIMER));

The tip tree managed code has rules for variable declarations (and more):

  https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#variable-declarations

No need to send a v3, I fix it up this time.

Thanks,

        tglx