On Mon, 24 May 2010, Arve Hjønnevåg wrote: > > Wakeup events can be lost in at least three different ways: > > > > 1. A hardware signal (such as an IRQ) gets ignored. > > > > 2. The hardware event occurs, but without effect since the > > kernel thread that would handle the event has been frozen. > > The event just ends up sitting in a queue somewhere until > > something else wakes up the system. > > > > 3. The hardware event occurs and the kernel handles it fully, > > but the event propagates to userspace for further handling > > and the user program is already frozen. > > > > 1 is a hardware configuration failure (for example, it might happen as > > a result of using edge-triggered IRQs instead of level-triggered) and > > is outside the scope of this discussion. > > > > 2 generally represents a failure of the core PM subsystem, or a failure > > of some other part of the kernel to use the PM core correctly. In > > theory we should be able to fix such mistakes. Right now I'm aware of > > at least one possible failure scenario that could be fixed fairly > > easily. > > > > 3 is the type of failure that suspend blockers were really meant to > > handle, particularly the userspace suspend-blocker API. > I don't see a big difference between 2 and 3. You can use suspend > blockers to handle either. You can, but they aren't necessary. If 2 were the only reason for suspend blockers, I would say they shouldn't be merged. Whereas 3, on the other hand, can _not_ be handled by any existing mechanism. 3 is perhaps the most important reason for using suspend blockers. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
