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SubjectRe: [patch] genirq/MSI: restore __do_IRQ() compat logic temporarily
On 09:50 Tue 12 Sep 2006, Ingo Molnar wrote:
> * Eric W. Biederman <ebiederm@xmission.com> wrote:
> > 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.
>
> indeed ... We thought the MSI cleanup went all the way with the irqchips
> conversion, that's we suggested to Andrew to drop this chunk in -mm too.
>
> > Except for adding that hunk back in and breaking 4K stacks I don't
> > have an immediate fix.
>
> i've attached a bandaid patch for -mm below. Brandon, does this solve
> the crash you are seeing?

Indeed- this patch makes the system bootable.

I will keep up on the -mm tree as this conversion continues and let all
of you know if things break again :-)

Thanks,

Brandon

> ------------------>
> Subject: [patch] genirq/MSI: restore __do_IRQ() compat logic temporarily
> From: Ingo Molnar <mingo@elte.hu>
>
> restore the __do_IRQ() compat logic temporarily, until the MSI
> genirq conversion has been completed.
>
> disable 4KSTACKS temporarily too.
>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
> ---
> arch/i386/Kconfig.debug | 4 ++++
> arch/i386/kernel/irq.c | 5 +++++
> 2 files changed, 9 insertions(+)
>
> Index: linux-2.6.18-rc6-mm1/arch/i386/Kconfig.debug
> ===================================================================
> --- linux-2.6.18-rc6-mm1.orig/arch/i386/Kconfig.debug
> +++ linux-2.6.18-rc6-mm1/arch/i386/Kconfig.debug
> @@ -56,8 +56,12 @@ config DEBUG_RODATA
> portion of the kernel code won't be covered by a 2MB TLB anymore.
> If in doubt, say "N".
>
> +#
> +# FIXME: Disabled temporarily until the MSI genirq conversion is done!
> +#
> config 4KSTACKS
> bool "Use 4Kb + 4Kb for kernel stacks instead of 8Kb" if DEBUG_KERNEL
> + depends on n
> default y
> help
> If you say Y here the kernel will use a 4Kb stacksize for the
> Index: linux-2.6.18-rc6-mm1/arch/i386/kernel/irq.c
> ===================================================================
> --- linux-2.6.18-rc6-mm1.orig/arch/i386/kernel/irq.c
> +++ linux-2.6.18-rc6-mm1/arch/i386/kernel/irq.c
> @@ -83,6 +83,10 @@ fastcall unsigned int do_IRQ(struct pt_r
> }
> #endif
>
> + if (!irq_desc[irq].handle_irq) {
> + __do_IRQ(irq, regs);
> + goto out_exit;
> + }
> #ifdef CONFIG_4KSTACKS
>
> curctx = (union irq_ctx *) current_thread_info();
> @@ -123,6 +127,7 @@ fastcall unsigned int do_IRQ(struct pt_r
> #endif
> desc->handle_irq(irq, desc, regs);
>
> +out_exit:
> irq_exit();
>
> return 1;

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