On Monday, September 22, 2014 10:07:03 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() > -> timekeeping_suspend() > -> clockevents_notify(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 move the clockevents suspend/resume notification > out of the syscore_suspend step and explictly call them at the appropriate > time in the suspend/hibernation paths. I.e. timers are suspend _before_ > IRQs get disabled. And accordingly in the resume path. > > Signed-off-by: Soren Brinkmann <[email protected]> > --- > Hi, > > there was not a lot of discussion on the last submission. Just one comment > from > Rafael (https://lkml.org/lkml/2014/8/26/780), which - as I outlined in my > response, does not apply, IMHO, since the platform does not re-enable > interrupts.
Well, you just don't agree with it. The problem with your approach is that timer interrupts aren't actually as special as you think and any other IRQF_NO_SUSPEND interrupts would have caused similar issues to appear under specific conditions. The solution I would suggest and that actually covers all IRQF_NO_SUSPEND interrupts would be to use a wait_event() loop like the one in freeze_enter() (on top of the current linux-next or the pm-genirq branch of linux-pm.git), but wait for pm_abort_suspend to become true, to implement system suspend. Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
