[tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in crash path

Yinghai Lu yinghai at kernel.org
Thu Feb 16 16:53:29 EST 2012

On Thu, Feb 16, 2012 at 9:27 AM, Don Zickus <dzickus at redhat.com> wrote:

> So I think I figured it out.  I went through and commented out code in
> disable_local_APIC until I narrowed it down to the piece of code that
> needs to be disabled for it to work.
> Surprise, surprise... its LVTPC or perf! :-)  Actually it is the
> nmi_watchdog which uses perf.  My theory is NMIs are not disabled and one
> is generated by the local apic during decompression (just bad timing) and
> *splat*.
> Yinghai, you can probably prove this by
> echo 0 > /proc/sys/kernel/nmi_watchdog
> then do your kdump crash test.

yes.  that will make kdump crash working.


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