Commit 1d927c3b authored Aug 18, 2011 by Tejun Heo Committed by Jiri Kosina Aug 23, 2011

apm-emulation: use wait_event_freezable() instead of freezer_[do_not_]count()



vfork is moving away from freezer_[do_not_]count() one way or the
other leaving apm_ioctl() as the only user.  apm_ioctl() just wants to
wait for suspend/resume cycle to complete without hindering the
freezer.  Use wait_event_freezable() instead.

The only annoyance is that wait_event_freezable() wakes up with
-ERESTART if there are pending signals while apm_ioctl() wants to
ignore all signals until suspend is complete.  We can play with
@current->[real_]blocked but this is hardly a performance or latency
critical path - simply chill a bit on each iteration until
SUSPEND_DONE for unlikely cases where there are pending signals.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

parent 51414d41

drivers/char/apm-emulation.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -300,17 +300,13 @@ apm_ioctl(struct file *filp, u_int cmd, u_long arg)
		/*
		* Wait for the suspend/resume to complete. If there
		* are pending acknowledges, we wait here for them.
		* wait_event_freezable() is interruptible and pending
		* signal can cause busy looping. We aren't doing
		* anything critical, chill a bit on each iteration.
		*/
		freezer_do_not_count();

		wait_event(apm_suspend_waitqueue,
		as->suspend_state == SUSPEND_DONE);

		/*
		* Since we are waiting until the suspend is done, the
		* try_to_freeze() in freezer_count() will not trigger
		*/
		freezer_count();
		while (wait_event_freezable(apm_suspend_waitqueue,
		as->suspend_state == SUSPEND_DONE))
		msleep(10);
		break;
		case SUSPEND_ACKTO:
		as->suspend_result = -ETIMEDOUT;

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