linux-kernel - Re: oom-kill && frozen()

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Message-ID: <20131113174220.GQ21461@twins.programming.kicks-ass.net>
Date:	Wed, 13 Nov 2013 18:42:20 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tejun Heo <tj@...nel.org>, David Rientjes <rientjes@...gle.com>,
	David Laight <David.Laight@...LAB.COM>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Ingo Molnar <mingo@...nel.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: oom-kill && frozen()

On Wed, Nov 13, 2013 at 06:07:24PM +0100, Oleg Nesterov wrote:
> 	4. Finally, change try_to_wake_up() path to do
> 
> 		-	p->state = TASK_WAKING;
> 		+	p->state &= ~state;
> 		+	if (p->state & ~(TASK_DEAD | TASK_WAKEKILL | TASK_PARKED))
> 		+		return;
> 		+	else
> 		+		p->state = TASK_WAKING;
> 
> 	   IOW, if the task sleeps in, say, TASK_INTERRUPTIBLE | __TASK_FROZEN
> 	   then it need both try_to_wake_up(TASK_INTERRUPTIBLE) and
> 	   try_to_wake_up(__TASK_FROZEN) to wake up.

> Tejun, Peter, do you think this makes any sense? I am just curious, but
> "selective wakeup" looks potentially useful.

I've never looked at any of this freeze stuff, so I cannot comment too
much. However we should be very careful not to add too much to relative
hot paths for the relative rare case of freezing stuff.


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