On Sun, 6 Jun 2010, Matthew Garrett wrote: > The difference between idle-based suspend and opportunistic suspend is > that the former will continue to wake up for timers and will never be > entered if something is using CPU, whereas the latter will be entered > whenever no suspend blocks are held. The problem with opportunistic > suspend is that you might make the decision to suspend simultaneusly > with a wakeup event being received. Suspend blocks facilitate > synchronisation between the kernel and userspace to ensure that all such > events have been consumed and handld appropriately. Remember that suspend takes place in several phases, the first of which is to freeze tasks. The phases can be controlled individually by the process carrying out a suspend, and there's nothing to prevent you from stopping after the freezer phase. Devices won't get powered down, but Android uses aggressive runtime power management for its devices anyway. If you do this then the synchronization can be carried out entirely from userspace, with no need for kernel modifications such as suspend blockers. And since Android can reach essentially the same low-power state from idle as from suspend, it appears that they really don't need any kernel changes at all. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
