linux-kernel - Re: [PATCH 14/16] freezer: make freezing() test freeze conditions in effect instead of TIF

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Date:	Mon, 29 Aug 2011 17:56:40 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	rjw@...k.pl, paul@...lmenage.org, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 14/16] freezer: make freezing() test freeze conditions
	in effect instead of TIF_FREEZE

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.

Oleg.

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