linux-kernel - Re: [PATCH 4/7] cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER

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Message-ID: <20121022211822.GF5951@atj.dyndns.org>
Date:	Mon, 22 Oct 2012 17:18:22 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	rjw@...k.pl, linux-kernel@...r.kernel.org, lizefan@...wei.com,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org
Subject: Re: [PATCH 4/7] cgroup_freezer: don't stall transition to FROZEN for
 PF_NOFREEZE or PF_FREEZER_SKIP tasks

Hey,

On Mon, Oct 22, 2012 at 08:34:53PM +0200, Oleg Nesterov wrote:
> On 10/16, Tejun Heo wrote:
> >
> > cgroup_freezer doesn't transition from FREEZING to FROZEN if the
> > cgroup contains PF_NOFREEZE tasks or tasks sleeping with
> > PF_FREEZER_SKIP set.
> 
> And thus the patch looks like another bugfix to me.

It is but I'm not gonna send this one -stable.  Nobody has complained
yet and this is a userland visible behavior change, so I'd rather not
risk it.

> Just one question, and this question is offtopic again,
> 
> > Only kernel tasks can be non-freezable (PF_NOFREEZE)
> 
> Hmm. We seem to "leak" PF_NOFREEZE if a kernel thread execs?
> Perhaps do_execve_common() should do set_freezable() before return.
> 
> Or, at least, simply clear this flag along with PF_KTHREAD in
> flush_old_exec().

Ooh, ouch, definitely.  We should clear that.  Can you please make a
patch?

Thanks.

--
tejun
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