From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
matthltc@us.ibm.com, paul@paulmenage.org,
containers@lists.linux-foundation.org,
linux-pm@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] freezer: fix wait_event_freezable/__thaw_task races
Date: Sun, 11 Sep 2011 20:41:07 +0200 [thread overview]
Message-ID: <20110911184107.GA23918@redhat.com> (raw)
In-Reply-To: <20110911182953.GA22941@redhat.com>
On 09/11, Oleg Nesterov wrote:
>
> On 09/11, Tejun Heo wrote:
> >
> > On Thu, Sep 08, 2011 at 07:59:26PM +0200, Oleg Nesterov wrote:
> >
> > > > Yeap, with freezable_with_signal gone, this looks correct & simpler to
> > > > me
> > >
> > > I don't really understand this... set_freezable_with_signal() has a
> > > lot of problems, yes... But even if it wasn't removed this fix makes
> > > sense anyway, afaics.
> > >
> > > If freezable_with_signal caller does wait_event_freezable_timeout(),
> > > __retval becomes -ERESTARTSYS after freeze_task(). The next iteration
> > > will return 0 with the KERN_ERR message from schedule_timeout().
> >
> > Hmmm... but with the change, if a kthread gets TIF_SIGPENDING from
> > freezer and then thawed, it would not enter try_to_freeze() and thus
> > won't clear TIF_SIGPENDING.
>
> Ah yes, you are right, thanks. But once again, please note that in this
> case wait_event_freezable_timeout() is broken anyway.
OTOH, I forgot about wait_event_freezable(). It was racy, but mostly
worked. So yes, you are right, without "kill freezable_with_signal"
this patch is wrong.
I missed this, thanks.
Oleg.
next prev parent reply other threads:[~2011-09-11 18:44 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-02 18:27 [PATCHSET pm-freezer] freezer: fixes & simplifications Tejun Heo
2011-09-02 18:27 ` [PATCH 1/6] cgroup_freezer: fix freezer->state setting bug in freezer_change_state() Tejun Heo
2011-09-04 18:02 ` Oleg Nesterov
2011-09-04 18:11 ` Tejun Heo
2011-09-04 18:20 ` Oleg Nesterov
2011-09-02 18:27 ` [PATCH 2/6] freezer: set PF_NOFREEZE on a dying task right before TASK_DEAD " Tejun Heo
2011-09-02 18:27 ` [PATCH 3/6] freezer: restructure __refrigerator() Tejun Heo
2011-09-02 18:27 ` [PATCH 4/6] freezer: use lock_task_sighand() in fake_signal_wake_up() Tejun Heo
2011-09-02 18:27 ` [PATCH 5/6] freezer: remove unused @sig_only from freeze_task() Tejun Heo
2011-09-02 18:27 ` [PATCH 6/6] freezer: kill unused set_freezable_with_signal() Tejun Heo
2011-09-04 18:46 ` Oleg Nesterov
2011-09-05 2:33 ` Tejun Heo
2011-09-05 2:35 ` Tejun Heo
2011-09-05 16:21 ` Oleg Nesterov
2011-09-05 16:20 ` Oleg Nesterov
2011-09-06 3:28 ` Tejun Heo
2011-09-06 15:18 ` Oleg Nesterov
2011-09-06 15:25 ` Oleg Nesterov
2011-09-06 15:53 ` Tejun Heo
2011-09-07 18:21 ` [PATCH 0/1] freezer: fix wait_event_freezable/__thaw_task races Oleg Nesterov
2011-09-07 18:22 ` [PATCH 1/1] " Oleg Nesterov
2011-09-08 1:05 ` Tejun Heo
2011-09-08 17:59 ` Oleg Nesterov
2011-09-11 1:54 ` Tejun Heo
2011-09-11 18:29 ` Oleg Nesterov
2011-09-11 18:41 ` Oleg Nesterov [this message]
2011-09-08 18:01 ` [PATCH 6/6] freezer: kill unused set_freezable_with_signal() Matt Helsley
2011-09-11 1:37 ` Tejun Heo
2011-09-04 18:48 ` [PATCHSET pm-freezer] freezer: fixes & simplifications Oleg Nesterov
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