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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20110829163047.GA9973@redhat.com>
Date:	Mon, 29 Aug 2011 18:30:47 +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

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.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/