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

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Message-ID: <20250915153151.fPHJU6-d@linutronix.de>
Date: Mon, 15 Sep 2025 17:31:51 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
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 2025-09-15 11:49:37 [-0300], Luis Claudio R. Goncalves wrote:
> 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.

Either way, if this change introduces a problem then it affects RT as
today. So we should deal with this. If it is not a problem and it just
put pressure on an existing problem then it shouldn't be an issue.

> Luis

Sebastian