[PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq

[Don Zickus]

On Tue, Jan 31, 2012 at 02:08:29PM -0800, Eric W. Biederman wrote:
> > The problem is that although kdump tries to shutdown minimal hardware,
> > it still needs to disable the IO APIC.  This requires spinlocks which
> > may be held by another cpu.  This other cpu is being held infinitely in
> > an NMI context by kdump in order to serialize the crashing path.  Instant
> > deadlock.
> 
> Can you test to see if kexec on panic still needs to disable the IO
> APIC.  Last I looked we were close if not all of the way there to not
> needing to boot the kernel in pic mode?

Ok, so you just blindly remove disable_IO_APIC from
native_machine_crash_shutdown and re-run some panic tests on various
machines?  What about the disable_IO_APIC path in native_machine_shutdown?

Also, where could I look to see if that work was done?  Is that in the
ioapic setup code?

> 
> If we can skip the ioapic disable entirely we should be much more
> robust.

Agreed.

Cheers,
Don