Messages in this thread | | | Date | Wed, 25 Mar 2009 10:19:06 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH] clockevent: on resume program the next oneshot tick with the next actual event |
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Ian Campbell wrote: > When resuming a Xen domU we were seeing an issue where the timer ticks never > seemed to start up again. This was with CONFIG_NO_HZ=y, the Xen clocksource > has CLOCK_EVT_FEAT_ONESHOT but not CLOCK_EVT_FEAT_PERIODIC. > > The issue is that on resume tick_resume_oneshot() tries to program an event for > "now", e.g. > tick_program_event(ktime_get(), 1); > > However further down the call chain tick_dev_program_event() then compares that > Where's that? Do you mean in clockevents_program_event():
delta = ktime_to_ns(ktime_sub(expires, now));
if (delta <= 0) return -ETIME;
?
> expiry time with a second call to ktime_get() and discards the event if the > timeout is negative -- which it always will be since some time must have passed > since tick_program_event was called. > > Instead of asking for an immediate event on resume, instead ask for the next > actual event. >
What if the next event is now anyway? What timebase is it in anyway?
> With this fix I can successfully resume a Xen domain. >
That's good, but I think there's more going on here.
J
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