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

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Message-Id: <201110272221.06782.rjw@sisk.pl>
Date:	Thu, 27 Oct 2011 22:21:06 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	Pavel Machek <pavel@....cz>, trond.myklebust@...app.com,
	smfrench@...il.com, 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 Wednesday, October 26, 2011, Jeff Layton wrote:
> On Tue, 11 Oct 2011 21:14:28 +0200
> "Rafael J. Wysocki" <rjw@...k.pl> wrote:
> 
> > On Tuesday, October 11, 2011, Jeff Layton wrote:
> > > 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?
> > 
> > I will push it for 3.2.
> > 
> 
> Hi Rafael,
> 
> Trond asked if you would also be willing to push patches 3 and 4 in
> this series for 3.2 as well [1]? Note that patch #4 got another revision so
> we'll want to make sure that you get that one. I can resend the
> nfs/sunrpc patches if that will help...
> 
> [1]: I think Steve F is going to push patch #2, so that one shouldn't
> be an issue. 

Well, I've already sent my pull request.  I can keep these patches in my
tree for the next pull request, though (I'm sure there will be fixes against
3.2, so they will go along with those).

Thanks,
Rafael
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