Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 2 Mar 2023 16:00:52 +0100 | Subject | Re: [RFC][PATCH 2/2] time: alarmtimer: Use TASK_FREEZABLE to cleanup freezer handling |
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On Thu, Mar 2, 2023 at 1:48 AM John Stultz <jstultz@google.com> wrote: > > On Wed, Mar 1, 2023 at 2:11 PM Thomas Gleixner <tglx@linutronix.de> wrote: > > > > On Mon, Feb 27 2023 at 20:06, John Stultz wrote: > > > On Mon, Feb 27, 2023 at 4:03 PM John Stultz <jstultz@google.com> wrote: > > >> > On Mon, Feb 20 2023 at 19:11, Michael Nazzareno Trimarchi wrote: > > >> > +static int alarmtimer_pm_notifier_fn(struct notifier_block *bl, unsigned long state, > > >> > + void *unused) > > >> > +{ > > >> > + switch (state) { > > >> > + case PM_HIBERNATION_PREPARE: > > >> > + case PM_POST_HIBERNATION: > > >> > + atomic_set(&alarmtimer_wakeup, 0); > > >> > + break; > > >> > + } > > >> > + return NOTIFY_DONE; > > >> > > >> But here, we're setting the alarmtimer_wakeup count to zero if we get > > >> PM_HIBERNATION_PREPARE or PM_POST_HIBERNATION notifications? > > >> And Michael noted we need to add PM_SUSPEND_PREPARE and > > >> PM_POST_SUSPEND there for this to seemingly work. > > > > Yup. I missed those when sending out that hack. > > > > > So Thomas's notifier method of zeroing at the begining of suspend and > > > tracking any wakeups after that point makes more sense now. It still > > > feels a bit messy, but I'm not sure there's something better. > > > > I'm not enthused about it either. > > That said, it does work. :) In my testing, your approach has been > reliable, so it has that going for it. > > > > My only thought is this feels a little bit like its mirroring what the > > > pm_wakeup_event() logic is supposed to do. Should we be adding a > > > pm_wakeup_event() to alarmtimer_fired() to try to prevent suspend from > > > occuring for 500ms or so after an alarmtimer has fired so there is > > > enough time for it to be re-armed if needed? > > > > The question is whether this can be called unconditionally and how that > > interacts with the suspend logic. Rafael? > > I took a brief stab at this, and one thing is the test needs to use > the /sys/power/wakeup_count dance before suspending.
That's correct.
> However, I still had some cases where the recurring alarmtimer got > lost, so I need to dig a bit more to understand what was going wrong > there.
I'm interested in that too, so if you have any conclusions, please let me know.
> In the meantime, I'm ok with Thomas' approach, but we probably need > some comment documentation that suggests it might be reworked in a > cleaner way?
Well, in theory, the PM notifier can run in parallel with alarmtimer_fired() right after it has incremented the atomic var, can't it?
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