linux-kernel - Re: 2.6.18-rc6-mm1 2.6.18-rc5-mm1 Kernel Panic on X60s

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Date:	Tue, 12 Sep 2006 00:20:34 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...l.org>
Cc:	Brandon Philips <brandon@...p.org>, linux-kernel@...r.kernel.org,
	Brice Goglin <brice@...i.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Robert Love <rml@...ell.com>
Subject: Re: 2.6.18-rc6-mm1 2.6.18-rc5-mm1 Kernel Panic on X60s

Andrew Morton <akpm@...l.org> writes:

> OK, thanks.
>
> I don't think this necessarily tells us where the bug lies.  It could be
> some pre-existing thing in MSI, or it could be added by Bryce's changes. 
> Or by Eric's.  Or, of course, by
> genirq-convert-the-i386-architecture-to-irq-chips.patch.
>
> There doesn't seem to be a lot of movement on this and we want to get the
> x86 genirq conversion into 2.6.19.  Could be that we end up having to merge
> known-buggy stuff into mainline and crash enough computers to irritate
> someone into fixing it.  Rather sad.


Ok.  Looking at it I almost certain the problem is that
we lost the hunk of code removed in: 266f0566761cf88906d634727b3d9fc2556f5cbd
i386: Fix stack switching in do_IRQ

-       if (!irq_desc[irq].handle_irq) {
-               __do_IRQ(irq, regs);
-               goto out_exit;
-       }

The msi code does not yet set desc->handle_irq.  So when we attempt
to call it we get a NULL pointer dereference.

Except for adding that hunk back in and breaking 4K stacks I don't
have an immediate fix.

I do have a pending cleanup that should result in us setting handle_irq
in all cases.  I will see if I can advance that shortly.

Eric
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