Messages in this thread | | | Date | Fri, 5 Aug 2005 11:53:29 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 2.6.13-rc5-gitNOW] msleep() cannot be used from interrupt |
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Petr Vandrovec <vandrove@vc.cvut.cz> wrote: > > Since beginning of July my Opteron box was randomly crashing and being rebooted > by hardware watchdog. Today it finally did it in front of me, and this patch > will hopefully fix it. > > Problem is that at the end of June (28th, commit > 47f176fdaf8924bc83fddcf9658f2fd3ef60d573, [PATCH] Using msleep() instead of HZ) > rtc_get_rtc_time was converted to use msleep() instead of busy waiting. But > rtc_get_rtc_time is used by hpet_rtc_interrupt, and scheduling is not allowed > during interrupt. So I'm reverting this part of original change, replacing > msleep() back with busy loop. > > Original old code was busy waiting for 20ms, while on my hardware in the worst > case update-in-progress bit was asserted for at most 363 passes through loop > (on 2GHz dual Opteron), much less than even one jiffie, not even talking > about 20ms. So I changed code to just wait only as long as necessary. Otherwise > when RTC was set to generate 8192Hz timer, it stopped doing anything for > 20ms (160 pulses were skipped!) from time to time, and this is rather suboptimal > as far as I can tell.
That's all pretty sad stuff. I guess for now we can go back to the busy loop. Longer-term it would be nice if we could tune up the HPET driver in some manner so we can avoid this busy-wait-in-interrupt.
I'm not sure who the HPET maintainer/expert is nowadays. Robert Picco did the original work but I haven't seen Robert around for a long time? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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