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Date: Fri, 18 Sep 2026 13:33:49 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: "Shubhang Kaushik (Ampere)" <sh@gentwo.org>
Cc: Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
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	Dietmar Eggemann <dietmar.eggemann@arm.com>,
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	Valentin Schneider <vschneid@redhat.com>,
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	Shubhang Kaushik <shubhang@os.amperecomputing.com>,
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	Christopher Lameter <clameter@amperecomputing.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v2 1/2] sched: Document WF_SYNC wakeup placement
 semantics
Message-ID: <20260918113349.GM776954@noisy.programming.kicks-ass.net>
References: <20260917-sched-wf-sync-doc-v2-0-6d1f107c0596@gentwo.org>
 <20260917-sched-wf-sync-doc-v2-1-6d1f107c0596@gentwo.org>
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In-Reply-To: <20260917-sched-wf-sync-doc-v2-1-6d1f107c0596@gentwo.org>

On Thu, Sep 17, 2026 at 01:43:24PM -0700, Shubhang Kaushik (Ampere) wrote:
> WF_SYNC is supplied by callers that expect the waker to schedule away
> soon. The fair scheduler can use it as a placement and preemption hint,
> but its semantics are not documented.
> 
> Document the stable fair-class WF_SYNC semantics. WF_SYNC is advisory:
> it can influence placement and preemption, but does not guarantee CPU
> locality, avoidance of migration, or immediate wakee preemption.
> 
> This documents existing behavior only. It does not establish a new
> WF_SYNC placement policy.
> 
> Signed-off-by: Shubhang Kaushik (Ampere) <sh@gentwo.org>

*groan*, why not just a comment that goes with WF_SYNC? All this
documentation stuff is a dumping ground for bitrot.