linux-kernel - Re: PATCH/RFC: [kdump] fix APIC shutdown sequence

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Date:	Wed, 08 Aug 2007 20:22:54 +0200
From:	Martin Wilck <martin.wilck@...itsu-siemens.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"vgoyal@...ibm.com" <vgoyal@...ibm.com>,
	Haren Myneni <hbabu@...ibm.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: PATCH/RFC: [kdump] fix APIC shutdown sequence

Eric W. Biederman wrote:

>> I think a lot would be gained if disable_IO_APIC() would just mask the IRQs
>> (like the function in my patch does), and perhaps fix the dest ID, instead of
>> totally clearing the registers.
> 
> Even masked we still won't see the EOI, because then we are in i8259
> mode.  So masked versus totally cleared really should make no
> difference.

You are talking about EOI sent in the kdump kernel, correct? With my patch
the EOI (sent in the "old" kernel) is seen.

> I guess right now I can see work put into cleaning things up a little
> or not having to call disable_IO_APIC() at all.  that was supposed
> to be a short term hack, until we fixed things properly.
> 
> So far no one has been brave enough to mess with the kernel apic
> initialization order so we can remove disable_IO_APIC.  If our
> goal isn't to fix things properly by removing the need for
> disable_IO_APIC I don't feel like putting much effort into this
> code path.

Who is working on this? Can you give a reference to a list of things that
would need to be done to do this right?

Martin

-- 
Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DE6

Fujitsu Siemens Computers GmbH
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33106 Paderborn
Germany

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