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SubjectRe: [PATCH] clockevent: on resume program the next oneshot tick with the next actual event
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On Wed, 2009-03-25 at 19:40 -0400, Jeremy Fitzhardinge wrote:
> Ian Campbell wrote:
> > Hmm, yes I think so too. I misread tick_dev_program_event(), it seems
> > like it Does The Right Thing and I do see the Xen set_next_event hook
> > get called which I thought wasn't getting called earlier.
> >
> > Turns out the virtual timer IRQ isn't getting reinitialised before
> > tick_oneshot_resume runs so we are just missing the interrupt, doh!
> >
>
> While that ordering is a bug, I'm still not sure it completely explains
> what we're seeing here.
>
> In drivers/xen/manage.c:do_suspend() we call clock_was_set(), which has
> the specific effect of causing all the timer events to get retriggered
> on all cpus.

Not if CONFIG_HIGH_RES_TIMERS is not set, which I don't have. If I set
it then things work as expected even without the patch.

When CONFIG_HIGH_RES_TIMERS is set though the call to clock_was_set ends
up in hr_timer_force_reprogram, I'm not clear what the relationship
between hrtimers and ticks is, they both seem to call down to the
oneshot code eventually, so they must coexist somehow...

Ian.

> This is necessary because we don't unplug/replug all the
> cpus, and the normal sysdev_resume() timer resume only resumes the
> current cpu (which is cpu 0 in this case). It also deals with the
> clocksource timebase shifting, as it will over suspend/resume (esp
> suspend/reboot/resume, or suspend/migrate/resume). Your patch will only
> re-trigger the next cpu0 timer event, and leave the rest hanging without
> a next event.
>
> So the question is why does your patch help?
>
> I'm seeing much worse symptoms on my test machine: the resumed domain is
> just sitting there spinning dead with 100% cpu use. I don't know if
> this is related or something else.
>
> J
>
> > Subject: xen: resume interrupts before system devices.
> >
> > otherwise the first timer interrupt after resume is missed and we never
> > get another.
> >
> > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> >
> > diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
> > index 0489ea2..5269bb4 100644
> > --- a/drivers/xen/manage.c
> > +++ b/drivers/xen/manage.c
> > @@ -68,15 +68,15 @@ static int xen_suspend(void *data)
> > gnttab_resume();
> > xen_mm_unpin_all();
> >
> > - sysdev_resume();
> > - device_power_up(PMSG_RESUME);
> > -
> > if (!*cancelled) {
> > xen_irq_resume();
> > xen_console_resume();
> > xen_timer_resume();
> > }
> >
> > + sysdev_resume();
> > + device_power_up(PMSG_RESUME);
> > +
> > return 0;
> > }
> >
> >
> > Ian.
> >
> >
> >
> >
> >> J
> >> --
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> >>
> >>
> >
> >
>



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