APM: fix deadlock in APM_IOC_SUSPEND ioctl

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>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/char/apm-emulation.c b/drivers/char/apm-emulation.c
index f4837a893dfa..6005c5c03f2a 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: