linux-kernel - Re: [PATCH 7/7] sched: implement try_to_wake_up

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Message-ID: <1260262394.3935.981.camel@laptop>
Date:	Tue, 08 Dec 2009 09:53:14 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	tglx@...utronix.de, mingo@...e.hu, avi@...hat.com, efault@....de,
	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] sched: implement try_to_wake_up_local()

On Mon, 2009-12-07 at 19:27 +0900, Tejun Heo wrote:
> 
> > What happens when you run out of memory and the workqueue progress is
> > needed to get free memory?
> 
> That's when the "rescuer" workers kick in.  All workqueues which might
> be used during allocation paths are required to have one.  When
> manager fails to fork a new worker, it summons the rescuers.  They
> migrate to the distressed cpu and processes only the works from their
> specific workqueues thus guaranteeing forward progress.

What happens if the rescue worker is tied up on another cpu in a
deadlock avoidance game, which requires progress on this cpu in order to
resolve it?

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