On 07/21/2014 10:35 AM, Soren Brinkmann wrote: > On platforms that do not power off during suspend, successfully entering > suspend races with timers. > > The race happening in a couple of location is: > > 1. disable IRQs (e.g. arch_suspend_disable_irqs()) > ... > 2. syscore_suspend() > -> tick_suspend() (timers are turned off here) > ... > 3. wfi (wait for wake-IRQ here) > > Between steps 1 and 2 the timers can still generate interrupts that are > not handled and stay pending until step 3. That pending IRQ causes an > immediate - spurious - wake. > > The solution is to remove the timekeeping suspend/resume functions from > the syscore functions and explictly call them at the appropriate time in > the suspend/hibernation patchs. I.e. timers are suspend _before_ IRQs > get disabled. And accordingly in the resume path.
So.. I sort of follow this, though from the description disabling timekeeping to turn off timers seems a little indirect (I do see that suspending timekeeping calls clockevents_suspend() which is the key part). Maybe this could be clarified in a future version of the patch description? I worry that moving timekeeping_suspend earlier in the suspend process might cause problems where things access time in the suspend path. I recall these orderings have been problematic in the past, and slightly tweaking them can often destabilize things badly. I wonder if it would be better just to move the clockevent_suspend() call to the earlier site, that way timers are halted but timekeeping continues until its normal suspend point. thanks -john -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
