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

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Message-ID: <20120217195430.GO9751@redhat.com>
Date:	Fri, 17 Feb 2012 14:54:30 -0500
From:	Don Zickus <dzickus@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org,
	mingo@...hat.com, hpa@...or.com, torvalds@...ux-foundation.org,
	kexec@...ts.infradead.org, vgoyal@...hat.com,
	akpm@...ux-foundation.org, tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/debug] x86/kdump: No need to disable ioapic/ lapic in
 crash path

On Fri, Feb 17, 2012 at 04:41:01AM -0800, Eric W. Biederman wrote:
> 
> The fix with a guarantee of no more scope creep is to just disable the
> nmi watchdog on the kexec on panic path.
> 
> Don if you have time please figure out is needed to ignore nmi's and
> possible record and/or report them while we boot, otherwise please cook
> up a patch that just disables the nmi watchdog wherever we are sending
> it from (the local apic or the ioapic).

Can I keep things even simpler?  The original problem was the deadlock
with the ioapic lock.  We fixed that by removing the call to
disable_IO_APIC().  Can we just leave the disable_local_APIC calls in
there for now?  Is there any real harm?

All this rewrite is going to take time which will delay fixing a current
problem with kexec on panic, the ioapic deadlock.

Thoughts?

Cheers,
Don
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