linux-kernel - Re: [PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state setting bug in freezer_change

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Message-ID: <20110902173127.GA3083@htj.dyndns.org>
Date:	Sat, 3 Sep 2011 02:31:27 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Matt Helsley <matthltc@...ibm.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul Menage <paul@...lmenage.org>,
	containers@...ts.linux-foundation.org,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH pm-freezer 1/4] cgroup_freezer: fix freezer->state
 setting bug in freezer_change_state()

Hello,

On Fri, Sep 02, 2011 at 07:15:17PM +0200, Oleg Nesterov wrote:
> > I guess it depends on the viewpoint.  A simple analogy would be using
> > WARN_ON_ONCE() instead of BUG_ON() so that the mode of failure is
> > softer.  This change isn't likely to make bugs significantly more
> > difficult to discover so why not?
> 
> I agree either way.
> 
> Personally I prefer your current patch. Because it is not clear why
> do we call try_to_freeze_cgroup() if it was already called. And, the
> 2nd call can silently hide the problem if we have some bug.
> 
> But of course, this is up to you and Matt.

I'm okay either way too.  It would make a bug in that area a bit less
annoying and thus may decrease the chance of bug report, but it means
that we ship with built-in easy work around (if it doesn't work at the
first kick, kick again), which can be beneficial in practice.

> > > But I agree either way. Rafael, I think 1-4 are fine, but I think
> > > we need the simple 5/4, will send in a minute...
> >
> > Can you please wait a bit?  The second one was broken (missing unlock)
> 
> Yes, I just noticed the small problem too, hopefully we mean the same
> bug ;)

Yeap, the same one.  I thought it was the second patch instead of the
third. :)

Thanks.

-- 
tejun
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