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

[ebiederm@xmission.com (Eric W. Biederman)]

Andrew Morton <akpm@osdl.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