On Thu, Aug 5, 2010 at 7:22 AM, <david@xxxxxxx> wrote: > > Ok, it is now sounding to me like there are two different (but somewhat > related) purposes that wakelocks are being used for > > 1. deciding if the system should go to sleep now or not (what most of the > discussion has been about) > > 2. narrowing the race between going to sleep and wakeup events. > > I'm not sure it's possible to completely eliminate the race, even with > wakelocks there is some time between the time you last check if the wakelock > is set and when the hardware finishes responding to your commands to go to > sleep (Unless you can set a level-based interrupt that will wake you up as > soon as you finish going to sleep) The transition into sleep is race-free in the wakelock model -- either the wakeup event happens during the kernel suspend (and grabs a wakelock), in which case suspend is aborted (and not attempted again until there are once again no more wakelocks held), or the system fully suspends to its lowest power mode until a wakeup event brings it back out again. Entry to lowest power mode must abort if a wakeup event/interrupt occurs while it's in process -- exactly how the handoff happens here is hardware dependent but in practice this is doable on just about any modern system. Brian _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
