Re: Race in vt_event_wait() during suspend/resume

Greg KH
2012-05-18T18:06:35Z

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@rab.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