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Date: Mon, 29 Aug 2011 18:30:47 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: rjw@sisk.pl, paul@paulmenage.org, linux-kernel@vger.kernel.org,
        arnd@arndb.de
Subject: Re: [PATCH 14/16] freezer: make freezing() test freeze conditions
	in effect instead of TIF_FREEZE
Message-ID: <20110829163047.GA9973@redhat.com>
References: <1313763382-12341-1-git-send-email-tj@kernel.org> <1313763382-12341-15-git-send-email-tj@kernel.org> <20110829154944.GA7531@redhat.com> <20110829155640.GA8392@redhat.com>
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On 08/29, Oleg Nesterov wrote:
>
> I'm afraid I wasn't clear....
>
> On 08/29, Oleg Nesterov wrote:
> >
> > On 08/19, Tejun Heo wrote:
> > >
> > > @@ -311,9 +315,11 @@ static int freezer_change_state(struct cgroup *cgroup,
> > >
> > >  	switch (goal_state) {
> > >  	case CGROUP_THAWED:
> > > +		atomic_dec(&system_freezing_cnt);
> > >  		unfreeze_cgroup(cgroup, freezer);
> > >  		break;
> > >  	case CGROUP_FROZEN:
> > > +		atomic_inc(&system_freezing_cnt);
> >
> > This is harmless, but afaics is not exactly right. CGROUP_FROZEN doesn't
> > need system_freezing_cnt != 0, everything is already frozen and we just
> > provoke freezing_slow_path() without any reason. Right?
>
> Of course, this atomic_inc() is right, we are going to call
> try_to_freeze_cgroup(). But probably it makes sense to do atomic_dec()
> when freezer->state becomes CGROUP_FROZEN.

Damn, I was wrong again.

No, we can't do this. __refrigerator() should handle the spurious
wakeups correctly, it checks checks freezing() in the main loop.

Oleg.