linux-kernel - Re: [PATCH]: Fix assertion failure with MSI on sparc64

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Message-Id: <1178937044.10759.20.camel@concordia.ozlabs.ibm.com>
Date:	Sat, 12 May 2007 12:30:44 +1000
From:	Michael Ellerman <michael@...erman.id.au>
To:	David Miller <davem@...emloft.net>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH]: Fix assertion failure with MSI on sparc64

On Fri, 2007-05-11 at 13:26 -0700, David Miller wrote:
> Hi Michael, I'm still working through the various regressions on
> sparc64 added by your MSI changes :-)

Hi Dave,

Guilty as charged - I did CC you on the patches though ;)

> The one I fixed the other day was a missed switch over to
> alloc_pci_dev() in the sparc64 PCI probing code which caused an OOPS
> in pci_enable_msi() because the list head of the pci dev was not
> initialized.  PowerPC's OBP firmware tree based PCI probing code
> was updated, sparc64's wasnt.

Sorry - not sure how I missed that one, it even matches
"k.alloc(.*pci_dev" - thanks for fixing it :)

> Today's find is a triggered assertion in msi_free_irqs() when the
> system doesn't support MSI, in which case arch_setup_msi_irqs() always
> returns an error.

What do you need to determine that the system can't support MSI? Could
you do that logic in arch_msi_check_device()?

> The problem is that when this happens we branch into msi_free_irqs(),
> to which you added the following assertion loop:
> 
> 	list_for_each_entry(entry, &dev->msi_list, list)
> 		BUG_ON(irq_has_action(entry->irq));
> 
> Well, if arch_setup_msi_irqs() fails, entry->irq will be zero and
> although that's never assigned to any normal devices we use that IRQ
> number for the timer interrupt on sparc64 so this assertion triggers.
> 
> Better to test for zero before doing the irq_has_action() assertion
> thing.

Yep, looks good - it matches the logic in arch_teardown_msi_irqs().

cheers


Acked-by: Michael Ellerman <michael@...erman.id.au>

> Signed-off-by: David S. Miller <davem@...emloft.net>
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index e6740d1..d9cbd58 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -549,8 +549,10 @@ static int msi_free_irqs(struct pci_dev* dev)
>  {
>  	struct msi_desc *entry, *tmp;
>  
> -	list_for_each_entry(entry, &dev->msi_list, list)
> -		BUG_ON(irq_has_action(entry->irq));
> +	list_for_each_entry(entry, &dev->msi_list, list) {
> +		if (entry->irq)
> +			BUG_ON(irq_has_action(entry->irq));
> +	}
>  
>  	arch_teardown_msi_irqs(dev);
>  
-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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