Messages in this thread | | | Date | Mon, 8 Feb 2010 12:39:06 +0300 | Subject | Re: [PATCH 3/3 v2] nmi_watchdog: config option to enable new nmi_watchdog | From | Cyrill Gorcunov <> |
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On 2/8/10, Ingo Molnar <mingo@elte.hu> wrote: > > * Don Zickus <dzickus@redhat.com> wrote: > >> +config NMI_WATCHDOG >> + bool "Detect Hard Lockups with an NMI Watchdog" >> + depends on DEBUG_KERNEL && PERF_EVENTS >> + default y >> + help >> + Say Y here to enable the kernel to use the NMI as a watchdog >> + to detect hard lockups. This is useful when a cpu hangs for no >> + reason but can still respond to NMIs. A backtrace is displayed >> + for reviewing and reporting. >> + >> + The overhead should be minimal, just an extra NMI every few >> + seconds. > > Thought for later patches: I think an architecture should be able to express > via a Kconfig switch that it actually _has_ NMI events. There's > architectures > which dont have a PMU driver and only have software events. There's also > architectures that have a PMU driver but no NMIs. > > Something like ARCH_HAS_NMI_PERF_EVENTS? > > Also, i havent checked, but what is the practical effect of the new generic > watchdog on x86 CPUs that does not have a native PMU driver yet - such as > P4s? >
p4 pmu is not yet implemented. I'll try to post on lkml the thnigs i've done for it today evening, though it's pretty ugly i would say.
> Anyway, i'll create a tip:perf/nmi topic branch for these patches, it > certainly looks like a useful generalization and a new architecture that has > perf could easily enable it, without having to write its own NMI watchdog > implementation. It's also useful for any new watchdog features that people > might want to add. Plus it makes the x86 PMU code cleaner in the long run as > well. > > Thanks, > > Ingo >
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