linux-kernel - Re: [PATCH 1/4] freezer: make fake_signal_wake_up wake TASK

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Message-ID: <20111011061000.3a3a03fe@tlielax.poochiereds.net>
Date:	Tue, 11 Oct 2011 06:10:00 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	Pavel Machek <pavel@....cz>
Cc:	trond.myklebust@...app.com, smfrench@...il.com, rjw@...k.pl,
	linux-pm@...ts.linux-foundation.org, linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org, john@...va.COM,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] freezer: make fake_signal_wake_up wake
 TASK_KILLABLE tasks too

On Tue, 11 Oct 2011 08:18:48 +0200
Pavel Machek <pavel@....cz> wrote:

> 
> Hi!
> 
> > TASK_KILLABLE is often used to put tasks to sleep for quite some time.
> > One of the most common uses is to put tasks to sleep while waiting for
> > replies from a server on a networked filesystem (such as CIFS or NFS).
> > 
> > Unfortunately, fake_signal_wake_up does not currently wake up tasks
> > that are sleeping in TASK_KILLABLE state. This means that even if the
> > code were in place to allow them to freeze while in this sleep, it
> > wouldn't work anyway.
> > 
> > This patch changes this function to wake tasks in this state as well.
> > This should be harmless -- if the code doing the sleeping doesn't have
> > handling to deal with freezer events, it should just go back to sleep.
> 
> I'm pretty sure this will break something; but that does not mean it
> is bad idea, just that it should be merged early and tested a lot.
> 

FWIW, I looked at most of the places in the kernel that do
TASK_KILLABLE sleeps and they look like they'll handle this correctly.
The main one I wasn't sure about was mem_cgroup_handle_oom(), but I
think it'll do the right thing too. I certainly could have missed
something though...

In any case, would you mind merging this via the linux-pm tree for 3.2?

Thanks,
-- 
Jeff Layton <jlayton@...hat.com>
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