linux-kernel - Re: [RESEND PATCH] sched: restore the behavior of put_task

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Message-ID: <aMgngWdtqUKuqLcw@uudg.org>
Date: Mon, 15 Sep 2025 11:49:37 -0300
From: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Peter Zijlstra <peterz@...radead.org>, Oleg Nesterov <oleg@...hat.com>,
	Clark Williams <clrkwllms@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>,
	David Vernet <dvernet@...a.com>, Barret Rhoden <brho@...gle.com>,
	Josh Don <joshdon@...gle.com>, Crystal Wood <crwood@...hat.com>,
	linux-kernel@...r.kernel.org, linux-rt-devel@...ts.linux.dev,
	Juri Lelli <juri.lelli@...hat.com>, Ben Segall <bsegall@...gle.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wander Lairson Costa <wander@...hat.com>
Subject: Re: [RESEND PATCH] sched: restore the behavior of put_task_struct()
 for non-rt

On Mon, Sep 15, 2025 at 02:24:44PM +0200, Sebastian Andrzej Siewior wrote:
> On 2025-09-15 13:38:12 [+0200], Peter Zijlstra wrote:
> > Right, but I thought we did want to make this behaviour consistent.
> 
> That is correct, that is what I asked for (either consistent or a
> compelling reason why not).

I received a ping from colleagues investigating a problem possible caused
by excessive pressure on RCU and this change could make the problem worse.
But last I heard from them, sounds like the problem they are investigating
lies elsewhere.

That said, I don't have problems either way, limiting the change to RT or
keeping it general. I will follow whatever guidance I get from you all.

Luis

> Oleg pointed out that the patch description does not match the change.
> That is the only complaint.
> 
> > And IIRC RT has been running with this for ages, and never seen a
> > problem.
> 
> The syz-bot picked up RT recently. Other than that, yes, RT had it for
> ages.
> 
> Sebastian
> 
---end quoted text---