linux-kernel - Re: [PATCH] freezer,sched: Rewrite core freezer logic

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Message-ID: <20210615213518.GC4272@worktop.programming.kicks-ass.net>
Date:   Tue, 15 Jun 2021 23:35:18 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     rjw@...ysocki.net, mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        Will Deacon <will@...nel.org>, Tejun Heo <tj@...nel.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH] freezer,sched: Rewrite core freezer logic

On Tue, Jun 15, 2021 at 05:45:39PM +0200, Oleg Nesterov wrote:

> But this reminds me... can't we implement selective wakeups? So that if a
> task T sleeps in state = STOPPED | FROZEN, then ttwu(T, FROZEN) won't wake
> it up, it will only clear FROZEN from T->state. Similarly, ttwu(T, STOPPED)
> will leave this task with state == FROZEN.

All this started because I didn't want to touch the wakeup path for
freezing :/

> See also
> 
> 	https://lore.kernel.org/lkml/20131112162136.GA29065@redhat.com/
> 	https://lore.kernel.org/lkml/20131113170724.GA17739@redhat.com/
> 
> just to remind you that we already discussed TASK_FROZEN a little bit almost
> 10 years ago ;)
> 
> What has been shall be, and what has been done is what will be done, and
> there is nothing new under the sun.

Ha!, I had completely forgotten.