Messages in this thread | | | Subject | Re: __rtc_read_alarm missing month/year field bug? | From | Joe Lawrence <> | Date | Thu, 21 Jul 2016 15:52:02 -0400 |
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On 07/19/2016, Alexandre Belloni wrote: > > Well like said in my previous mail, I don't think the rollover is the > issue here but I'm interested in knowing what conditions are leading > to endless interrupts.
Hi Alexandre,
Unfortunately I've switched employers so I no longer have access to the hardware, but if I remember correctly the scenario went like this:
- boot machine with RTC alarm set in far future - run 'hwclock' user program - hwclock sync to clock tick - RTC_UIE_ON - RTC_UIE_OFF - kernel sees RTC alarm is outstanding - hpet_rtc_interrupt's start streaming in
In the case of this hardware platform, there was a problem with the CMOS RTC read such that hpet_rtc_interrupt / rtc_cmos_read believed that the RTC was busy updating ... that code would delay long enough that the next HPET rtc interrupt would come in right behind it and choke the CPU from scheduling anything else.
That platform-specific bug aside, I thought I would report this strangeness in case it was a real bug -- looks like I didn't fully consider the rollover case.
-- Joe
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