Messages in this thread | | | Date | Mon, 29 Mar 2010 13:04:18 -0400 | From | Yury Polyanskiy <> | Subject | Re: [PATCH] hangcheck-timer is broken on x86 |
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On Mon, 29 Mar 2010 09:43:27 -0700 john stultz <johnstul@us.ibm.com> wrote:
> > I am not sure which archs do you mean. But in any case, > > getrawmonotonic() is not just a wrap around a call to rdtsc() (or acpi > > pm timer read). It is based on the clock->raw_time, which is updated > > every timer interrupt by the update_wall_time(). So even if underlying > > timer wraps, it doesn't lead to getrawmonotonic() returning 0 sec. > > What I'm saying is that if you're using getrawmonotonic() to detect > hangs, you might miss them, as getrawmonotonic may wrap (and thus stop > continually increasing) if the timer interrupt is delayed. This does not > apply to systems using the TSC clocksource, but does apply to systems > using the acpi_pm.
But if timer interrupt is delayed by more than acpi_pm wrap-around time, then the update_wall_time() is also screwed. Since it is not, we can rely on getrawmonotonic().
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