linux-kernel - Re: [PATCH] sched/core: Remove double update_rq_clock() in __set_cpus_allowed_ptr

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Message-ID: <20251030091415.GH4067720@noisy.programming.kicks-ass.net>
Date: Thu, 30 Oct 2025 10:14:15 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: K Prateek Nayak <kprateek.nayak@....com>
Cc: Hao Jia <jiahao.kernel@...il.com>, mingo@...hat.com, mingo@...nel.org,
	juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
	Hao Jia <jiahao1@...iang.com>
Subject: Re: [PATCH] sched/core: Remove double update_rq_clock() in
 __set_cpus_allowed_ptr_locked()

On Thu, Oct 30, 2025 at 09:34:00AM +0530, K Prateek Nayak wrote:
> Hello Hao,
> 
> On 10/29/2025 3:06 PM, Hao Jia wrote:
> > From: Hao Jia <jiahao1@...iang.com>
> > 
> > Since commit d4c64207b88a ("sched: Cleanup the sched_change NOCLOCK usage"),
> > update_rq_clock() is called in do_set_cpus_allowed() -> sched_change_begin()
> > to update the rq clock. This results in a duplicate call update_rq_clock()
> > in __set_cpus_allowed_ptr_locked().
> > 
> > While holding the rq lock and before calling do_set_cpus_allowed(),
> > there is nothing that depends on an updated rq_clock.
> 
> I couldn't spot any dependency on rq_clock() until do_set_cpus_allowed()
> either so please feel free to include:
> 
> Reviewed-by: K Prateek Nayak <kprateek.nayak@....com>

Indeed, thanks!