linux-kernel - Re: [PATCH V7 0/9] SCHED_DEADLINE server infrastructure

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Message-ID: <20240729103253.GE37996@noisy.programming.kicks-ass.net>
Date: Mon, 29 Jul 2024 12:32:53 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vineeth Remanan Pillai <vineeth@...byteword.org>
Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org,
	Luca Abeni <luca.abeni@...tannapisa.it>,
	Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
	Thomas Gleixner <tglx@...utronix.de>,
	Joel Fernandes <joel@...lfernandes.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Phil Auld <pauld@...hat.com>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Youssef Esmat <youssefesmat@...gle.com>
Subject: Re: [PATCH V7 0/9] SCHED_DEADLINE server infrastructure

On Fri, Jun 21, 2024 at 10:41:35AM -0400, Vineeth Remanan Pillai wrote:

> Sorry that I could not get to reviewing and testing this revision. In
> v6 we had experienced a minor bug where suspend/resume had issues with
> dlserver. Since suspend does not do dequeue, dlserver is not stopped
> and this causes the premature wakeups. I haven't looked at v7 in
> detail, but I think the issue might still be present.

It is not.

> We have a workaround patch for this in our 5.15 kernel 

That is the problem... your necro kernel doesn't yet have the freezer
rewrite I imagine:

  f5d39b020809 ("freezer,sched: Rewrite core freezer logic")

That would cause all frozen tasks to be dequeued, and once all tasks
are dequeued, the deadline server stops itself too.

Juri did some testing to double check and no suspend / resume issues
were found.

Anyway, I've merged the lot into tip/sched/core.

Thanks all!