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Message-ID: <20120518180628.GA27021@kroah.com>
Date: Fri, 18 May 2012 11:06:28 -0700
From: Greg KH <gregkh@...uxfoundation.org>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Rabin Vincent <rabin@....in>, alan@...ux.intel.com,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: Race in vt_event_wait() during suspend/resume
On Fri, May 18, 2012 at 12:40:51PM +0100, Alan Cox wrote:
> On Fri, 18 May 2012 16:34:53 +0530
> Rabin Vincent <rabin@....in> wrote:
>
> > pm_restore_console() is called from the suspend/resume path,
> > this calls vt_move_to_console(), which calls vt_event_wait().
> >
> > There's a race in this path which causes the process
> > which requests the suspend to sleep indefinitely waiting
> > for an event which already happened:
> >
> > P1 P2
> > vt_move_to_console()
> > set_console()
> > schedule_console_callback()
> > vt_waitactive()
> > check n == fg_console +1
> > console_callback()
> > switch_screen()
> > vt_event_post() // no waiters
> >
> > vt_event_wait() // forever
> >
> > I think the following should fix it. Comments?
> >
>
> Looks right to me.
Great, Rabin, care to resend it with a proper Signed-off-by: line so
that I can apply it?
thanks,
greg k-h
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