linux-kernel - Re: 2.6.25-rc8-mm1 panic in rpaphp_register

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Message-Id: <20080415173656.218a6080.akpm@linux-foundation.org>
Date:	Tue, 15 Apr 2008 17:36:56 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alex Chiang <achiang@...com>
Cc:	pbadari@...ibm.com, linux-kernel@...r.kernel.org,
	linas@...tin.ibm.com
Subject: Re: 2.6.25-rc8-mm1 panic in rpaphp_register_slot()

On Mon, 7 Apr 2008 17:42:55 -0600
Alex Chiang <achiang@...com> wrote:

> Hi Badari,
> 
> > > > pci_hotplug: PCI Hot Plug PCI Core version: 0.5
> > > > rpaphp: RPA HOT Plug PCI Controller Driver version: 0.1
> > > > rpaphp_register_slot registering slot:path[/pci@...000020000003/pci@2,4] index[22010003], name[U787E.001.AAA3015-P2-C1] pdomain[22010003] type[16]
> > > > Unable to handle kernel paging request for data at address 0x00000070
> > > 
> > > Hrm, this is a little more information, but still not quite
> > > enough. I'm going to take a stab in the dark and say I'm probably
> > > doing something wrong on this line, maybe dereferencing a pointer
> > > incorrectly:
> > > 
> > >         retval = pci_hp_register(php_slot, slot->bus,
> > > 				 PCI_SLOT(PCI_DN(slot->dn->child)->devfn));
> > 
> > Sorry. I thought you knew this already. Disassembly clearly showed
> > that slot->dn->child is NULL. 
> > 
> > I confirmed it by adding printk also.
> 
> This patch is a complete guess on my part (since I've not been
> able to understand pseries architecture) but I think it should
> fix your issue.
> 
> Can you give it a try and let me know? It applies on top of the
> -mm tree that includes my physical pci_slot series.
> 
> Also, I'm hoping Linas will speak up and let me know what the
> real answer might be. ;)
> 
> Thanks.
> 
> /ac
> 
> From: Alex Chiang <achiang@...com>
> Subject: rpaphp: correctly call pci_hp_register for empty PCI slots
> 
> Unpopulated device_node slots do not have children, and
> attempting to dereference them will result in a panic.
> 
> Instead, attempt to derive the PCI slot number from the bus
> itself, and failing that, default to 0.
> 
> Signed-off-by: Alex Chiang <achiang@...com>
> ---
> diff --git a/drivers/pci/hotplug/rpaphp_slot.c b/drivers/pci/hotplug/rpaphp_slot.c
> index 0d4cfc7..91ce6a6 100644
> --- a/drivers/pci/hotplug/rpaphp_slot.c
> +++ b/drivers/pci/hotplug/rpaphp_slot.c
> @@ -121,6 +121,7 @@ int rpaphp_register_slot(struct slot *slot)
>  {
>  	struct hotplug_slot *php_slot = slot->hotplug_slot;
>  	int retval;
> +	int slot_nr;
>  
>  	dbg("%s registering slot:path[%s] index[%x], name[%s] pdomain[%x] type[%d]\n", 
>  		__FUNCTION__, slot->dn->full_name, slot->index, slot->name, 
> @@ -132,8 +133,11 @@ int rpaphp_register_slot(struct slot *slot)
>  		return -EAGAIN;
>  	}	
>  
> -	retval = pci_hp_register(php_slot, slot->bus,
> -				 PCI_SLOT(PCI_DN(slot->dn->child)->devfn));
> +	if (slot->bus->self)
> +		slot_nr = PCI_SLOT(slot->bus->self->devfn);
> +	else
> +		slot_nr = 0;
> +	retval = pci_hp_register(php_slot, slot->bus, slot_nr);
>  	if (retval) {
>  		err("pci_hp_register failed with error %d\n", retval);
>  		return retval;

Did we hear back from Badari on this?

Thanks.
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