lkml.org 
[lkml]   [2012]   [Apr]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Subject: [PATCH] APM: fix deadlock in APM_IOC_SUSPEND ioctl
On Sun, 1 Apr 2012, NeilBrown wrote:

>
>
> I found the Xorg server on my ARM device stuck in the 'msleep()' loop
> in apm_ioctl.
>
> I suspect it had attempted suspend immediately after resuming and lost
> a race.
> During that msleep(10);, a new suspend cycle must have started and
> changed ->suspend_state to SUSPEND_PENDING, so it was never seen to
> be SUSPEND_DONE and the loop could never exited. It would have moved on
> to SUSPEND_ACKTO but never been able to reach SUSPEND_DONE.
>
> So change the loop to only run while SUSPEND_ACKED rather than until
> SUSPEND_DONE. This is much safer.
>
> Signed-off-by: NeilBrown <neilb@suse.de>
>
> diff --git a/drivers/char/apm-emulation.c b/drivers/char/apm-emulation.c
> index f4837a8..6005c5c 100644
> --- a/drivers/char/apm-emulation.c
> +++ b/drivers/char/apm-emulation.c
> @@ -302,7 +302,7 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg)
> * anything critical, chill a bit on each iteration.
> */
> while (wait_event_freezable(apm_suspend_waitqueue,
> - as->suspend_state == SUSPEND_DONE))
> + as->suspend_state != SUSPEND_ACKED))
> msleep(10);
> break;
> case SUSPEND_ACKTO:

Good catch Neil! I have missed this race when we were moving away from
freezer_*_count() to wait_event_freezable() here.

Applied, thanks.

--
Jiri Kosina
SUSE Labs


\
 
 \ /
  Last update: 2012-04-03 03:47    [W:0.221 / U:0.044 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site