From f283d22713b0bdc147097c92c9b45855339cf1c8 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Sun, 1 Apr 2012 20:19:30 +1000 Subject: [PATCH] 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 Signed-off-by: Jiri Kosina --- drivers/char/apm-emulation.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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: