Messages in this thread Patch in this message | | | Date | Thu, 05 Apr 2012 08:27:13 -0400 | From | Prarit Bhargava <> | Subject | Re: [PATCH] clocksource, prevent overflow in clocksource_cyc2ns |
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> > So what kernel version are you using?
I retested using top of the linux.git tree, running
echo 1 > /proc/sys/kernel/sysrq for i in `seq 10000`; do sleep 1000 & done echo t > /proc/sysrq-trigger
and I no longer see a problem. However, if I increase the number of threads to 1000/cpu I get
Clocksource %s unstable (delta = -429565427) Clocksource switching to hpet
> to narrow down if you're problem is currently present in mainline or only in > older kernels, as that will help us find the proper fix.
If I hack in (sorry for the cut-and-paste)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index c958338..f38b8d0 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -279,11 +279,16 @@ static void clocksource_watchdog(unsigned long data) continue; }
- wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->m - watchdog->mult, watchdog->shift); + /*wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog- + watchdog->mult, watchdog->shift);*/ + wd_nsec = mult_frac(((wdnow - cs->wd_last), watchdog->mult, + 1UL << watchdog->shift); + + /*cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) & + cs->mask, cs->mult, cs->shift);*/ + cs_nsec = mult_frac(((csnow - cs->cs_last), cs->mult, + 1UL << cs->shift);
- cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) & - cs->mask, cs->mult, cs->shift); cs->cs_last = csnow; cs->wd_last = wdnow;
then I don't see unstable messages.
I think the problem is still here but it only happens in extreme cases.
P.
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