Messages in this thread | | | Date | Wed, 25 Nov 2015 15:25:56 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH v3] alarmtimer: fix unexpected rtc interrupt when system resume from S3 |
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On Fri, 20 Nov 2015, John Stultz wrote:
> On Tue, Nov 17, 2015 at 4:08 AM, <zhuo-hao.lee@intel.com> wrote: > > From: zhuo-hao <zhuo-hao.lee@intel.com> > > > > Before the system go to suspend (S3), if user create a timer with clockid > > CLOCK_REALTIME_ALARM/CLOCK_BOOTTIME_ALARM and set a "large" timeout value > > to this timer. The function alarmtimer_suspend will be called to setup > > a timeout value to RTC timer to avoid the system sleep over time. However, > > if the system wakeup early than RTC timeout, the RTC timer will not be cleared. > > And this will cause the hpet_rtc_interrupt come unexpectedly until the RTC > > timeout. To fix this problem, just adding alarmtimer_resume to cancel the > > RTC timer. > > > > This was noticed because the HPET RTC emulation fires an interrupt every > > 16ms(=1/2^DEFAULT_RTC_SHIFT) up to the point where the alarm time is reached. > > This program always hits this situation(https://lkml.org/lkml/2015/11/8/326), > > if system wake up earlier than alarm time. > > So thanks for the extra context here, and again I don't have an > objection to this patch. > > Although from the earlier discussion it still isn't quite clear to me: > Why must the HPET RTC emulation need to fire the alarm every 16ms? Is > that not something that can be fixed?
We probably can fix it with some surgery. OTOH that stuff is fragile as hell and I rather avoid touching it, but I won't hinder someone brave enough doing it :)
> I just want to make sure we're not hiding a deeper issue.
It's not a deeper issue. It's a - admittedly dumb - implementation detail.
Thanks,
tglx
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