Hi John, Re-sending because VGER rejected my hipster HTML mail... sorry!
On Fri, Feb 10, 2017 at 10:49 AM, John Stultz <john.stu...@linaro.org> wrote: >> I see a few ways to fix it: >> >> 1. Create a wakeup_source for each timerfd, and if it's an alarm timer >> call >> __pm_stay_awake() in timerfd_triggered() and __pm_relax() in >> timerfd_read(). >> 2. call pm_system_wakeup() in alarmtimer_fired() >> 3. call `if (isalarm(ctx)) pm_system_wakeup();' in timerfd_triggered() >> 4. call __pm_wakeup_event(ws, 2 * MSECS_PER_SEC) in alarmtimer_fired() >> 5. call `if (isalarm(ctc)) __pm_wakeup_event(ws, 2 * MSECS_PER_SEC);' >> in >> timerfd_triggered() (using a static struct wakeup_source). [snip] >> * #4 Matches the current behavior of the "happy case" if and only if >> userspace is using the 'wakeup' system, otherwise doesn't change any >> behavior. But, I wonder how many people think the current behavior is a >> bug. [snip] > The approach you took in your patch looks basically ok to me, though I > > think the __pm_wakeup_event() method in #4 sounds safer, just to avoid > the problematic issue if no one is waiting on the fd. > > Though I worry I'm not quite understanding the con for that case > properly, so maybe you can clarify what concerns you there? The concern is born of my personal experience: I was ignorant of the "wakeup_count" protocol, and so I wasn't using it. Because of this __pm_wakeup_event() would not block a suspend because I never wrote to wakeup_count. On the other hand, method #2 will work unconditionally. -gabe
