On Mon, 21 Jun 2010 12:54:44 -0400 (EDT) Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 21 Jun 2010, Florian Mickler wrote: > > > > > > What happens if an event arrives just before you read > > > > > /sys/power/wakeup_count, but the userspace consumer doesn't realize > > > > > there is a new unprocessed event until after the power manager checks > > > > > it? > > > > > > > I think this is not the kernel's problem. In this approach the kernel makes it > > > > possible for the user space to avoid the race. Whether or not the user space > > > > will use this opportunity is a different matter. > > > > > > It is _not_ possible for userspace to avoid this race. Help from the > > > kernel is needed. > > > > It is possible if every (relevant) userspace program implements a > > callback for the powermanager to check if one of it's wakeup-sources > > got activated. > > > > That way the powermanager would read /sys/power/wakeup_count, then do > > the roundtrip to all it's registered users and only then suspend. > > After further thought, there's still a race: Ah, yes. That's what I meant in my other mail with 'how to determine that an wake event is in flight'. Read this too late. > Alan Stern Cheers, Flo _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
