linux-kernel - Re: [PATCH v2] sched: do not call __put_task_struct() on rt if pi_blocked

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Message-ID: <20250410153205.u92eJDos@linutronix.de>
Date: Thu, 10 Apr 2025 17:32:05 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@...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>, lclaudio00@...il.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>
Subject: Re: [PATCH v2] sched: do not call __put_task_struct() on rt if
 pi_blocked_on is set

On 2025-04-10 09:51:03 [+0200], Peter Zijlstra wrote:
> > I complained about this special RT case in put_task_struct() when it was
> > first got introduced. Couldn't we just just unconditionally do the RCU
> > put?
> 
> Yeah, please make it simpler, not more complex.

Just so we clear: simpler as in everyone does call_rcu() or RT does
always call_rcu() and everyone else __put_task_struct()? I mean we would
end up with one call chain I am just not sure how expensive it gets for
!RT.

Sebastian