From: Peter Zijlstra <peterz@infradead.org>
To: "Shubhang Kaushik (Ampere)" <sh@gentwo.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
K Prateek Nayak <kprateek.nayak@amd.com>,
Christopher Lameter <clameter@amperecomputing.com>,
Shubhang Kaushik <shubhang@os.amperecomputing.com>,
Madadi Vineeth Reddy <vineethr@linux.ibm.com>,
Shrikanth Hegde <sshegde@linux.ibm.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] sched: Clarify WF_SYNC wakeup semantics
Date: Thu, 24 Sep 2026 12:05:13 +0200 [thread overview]
Message-ID: <20260924100513.GE4121339@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260922-sched-wf-sync-doc-v3-1-23ebe9e27bef@gentwo.org>
On Tue, Sep 22, 2026 at 02:57:05PM -0700, Shubhang Kaushik (Ampere) wrote:
> The synchronous waitqueue wakeup comments currently state that a
> synchronous wakee will not be migrated to another CPU. This is not
> guaranteed by the scheduler wakeup path.
>
> WF_SYNC is an advisory hint that the caller expects the waker to
> schedule away soon. Scheduler classes may use it for placement or
> preemption, but callers must not rely on it to prevent migration,
> preserve CPU locality, or make the wakee run next.
>
> Keep this contract next to the flag definition, remove the stale
> waitqueue wording, and make the locked helper refer to the unlocked
> variant.
>
> ---
> Signed-off-by: Shubhang Kaushik (Ampere) <sh@gentwo.org>
> ---
Thanks!
next prev parent reply other threads:[~2026-09-24 10:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-22 21:57 Shubhang Kaushik (Ampere)
2026-09-24 10:05 ` Peter Zijlstra [this message]
2026-09-24 15:36 ` Shrikanth Hegde
2026-09-25 10:54 ` [tip: sched/core] " tip-bot2 for Shubhang Kaushik (Ampere)
2026-09-25 17:35 ` Shrikanth Hegde
2026-09-25 18:35 ` Ingo Molnar
2026-09-25 18:36 ` [tip: sched/core] sched/wait: " tip-bot2 for Shubhang Kaushik (Ampere)
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