linux-kernel - Re: [PATCH] thinkpad-acpi: fix potential suspend blocking issue

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Message-ID: <20130305180542.GA12738@redhat.com>
Date:	Tue, 5 Mar 2013 19:05:42 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org, ibm-acpi@....eng.br,
	ibm-acpi-devel@...ts.sourceforge.net,
	platform-driver-x86@...r.kernel.org, Aaron Lu <aaron.lu@...el.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] thinkpad-acpi: fix potential suspend blocking issue

On 03/05, Mandeep Singh Baines wrote:
>
> On Tue, Mar 5, 2013 at 9:48 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> > On 03/05, Mandeep Singh Baines wrote:
> >>
> >> @@ -2462,13 +2462,13 @@ static int hotkey_kthread(void *data)
> >>       unsigned int poll_freq;
> >>       bool was_frozen;
> >>
> >> +     set_freezable();
> >> +
> >>       mutex_lock(&hotkey_thread_mutex);
> >>
> >>       if (tpacpi_lifecycle == TPACPI_LIFE_EXITING)
> >>               goto exit;
> >>
> >> -     set_freezable();
> >> -
> >
> > I don't understand this code... but don't we have the same problem
> > with kthread_freezable_should_stop() below? It can call __refrigerator()
> > too under the same lock.
> >
>
> I don't think the lock is held at that point. There is an unlock right
> before entering the while loop and at the bottom of the loop.

Hmm... Afaics this is another lock, hotkey_thread_data_mutex. But
hotkey_thread_mutex is still held.

Oleg.

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