From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Nam Cao <namcao@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Mel Gorman <mgorman@suse.de>,
Shrikanth Hegde <sshegde@linux.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] smp: Suppress false DEBUG_PREEMPT warning in smp_call_on_cpu()
Date: Wed, 5 Nov 2025 09:48:08 +0100 [thread overview]
Message-ID: <20251105084808.7-nsQ6lT@linutronix.de> (raw)
In-Reply-To: <87ikfolvjx.fsf@yellow.woof>
On 2025-11-05 09:42:42 [+0100], Nam Cao wrote:
> >> +
> >> + /* suppress warnings from debug_smp_processor_id() */
> >
> > If you want to add a comment, what about something like
> >
> > /* Preserve not being migratable such as SMP variant does */
>
> Wouldn't it be a bit misleading? It's true that technically SMP variant
> is not migratable, but that's because it is a per-cpu thread, not
> because of migrate_disable(). To me, the comment sounds like that there
> is also a migrate_disable() in SMP variant.
A per-cpu thread ensures that the control flow can not migrate to
another CPU. This is also what stops debug_smp_processor_id() warnings
from work invoked from queue_work_on() vs queue_work().
> Nam
Sebastian
prev parent reply other threads:[~2025-11-05 8:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-24 7:07 Nam Cao
2025-10-24 14:08 ` Sebastian Andrzej Siewior
2025-11-05 8:42 ` Nam Cao
2025-11-05 8:48 ` Sebastian Andrzej Siewior [this message]
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