From: Thomas Gleixner <tglx@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>,
Amit Matityahu <amitmat@amazon.com>
Cc: anna-maria@linutronix.de, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, dwmw@amazon.co.uk, jonnyc@amazon.com,
abaransi@amazon.com, alonka@amazon.com, ronenk@amazon.com,
farbere@amazon.com
Subject: Re: [PATCH] timers/migration: Fix livelock in tmigr_handle_remote_up()
Date: Thu, 04 Jun 2026 14:23:45 +0200 [thread overview]
Message-ID: <87a4ta5wa6.ffs@fw13> (raw)
In-Reply-To: <aiFJLiWDIVaMQOoV@localhost.localdomain>
On Thu, Jun 04 2026 at 11:45, Frederic Weisbecker wrote:
> Le Wed, Jun 03, 2026 at 05:01:39PM +0000, Amit Matityahu a écrit :
>> Questions for maintainers:
>>
>> 1. What was the original rationale for the cpu != smp_processor_id()
>> check? There is no code comment, commit message explanation or anything
>> in the original patch's email discussion as to why
>> timer_expire_remote() is skipped for the local CPU.
>
> The rationale was about assuming that such an expired timerqueue actually
> reflected a timer that was handled locally already and so it could be safely
> discarded. So we could spare some locking.
Right, but the assumption would only be valid _if_ the jiffies value
which was used in run_timers(GLOBAL) is propagated into the remote
handling.
>> - if (cpu != smp_processor_id())
>> - timer_expire_remote(cpu);
>> + timer_expire_remote(cpu);
>
> Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
I'll add a comment to that for posterity.
next prev parent reply other threads:[~2026-06-04 12:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-03 17:01 [PATCH] timers/migration: Fix livelock in tmigr_handle_remote_up() Amit Matityahu
2026-06-04 9:45 ` Frederic Weisbecker
2026-06-04 12:23 ` Thomas Gleixner [this message]
2026-06-04 12:38 ` [tip: timers/urgent] " tip-bot2 for Amit Matityahu
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