Messages in this thread | | | Date | Sat, 27 Mar 2010 18:51:01 -0400 | Subject | Re: [PATCH] hangcheck-timer is broken on x86 | From | Yury Polyanskiy <> |
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On Sat, Mar 27, 2010 at 6:03 PM, Joel Becker <Joel.Becker@oracle.com> wrote: > On Fri, Mar 26, 2010 at 10:02:59PM -0400, Yury Polyanskiy wrote: >> Joel, just realized there is a slight mistake in what I said before. >> getrawmonotonic() is a refined jiffies (and actually resolves to >> get_cycles() on my system in the end). Thus it doesn't count while in >> suspend. However, jiffies-based timers (aka timer-wheel) are also >> stopped while in suspend. So getrawmonotonic() is the right call to >> check the precision of the jiffies-based timer (i.e. you dont need to >> make a correction by calling monotonic_to_bootbased()). > > It's OK to tell hangcheck-timer users that suspend is not > allowed. After all, you're running something that you don't want to see > hang.
Joel, what I am saying is exactly the opposite: it is totally ok to suspend-resume with hangcheck-timer (jiffies are stopped and so is getrawmonotonic() when system suspended).
> Is there a clock in the system that is a true wallclock? I'm > guessing, since getrawmonotonic() is get_cycles() based, that it doesn't > provide accurate time in the face of cpufreq changes. Is that true?
Of course, getrawmonotonic accounts for cpufreq changes (see arch/x86/kernel/tsc.c:time_cpufreq_notifier()).
Yury -- 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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