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SubjectRe: 2.6.25-rc8-mm1 panic in rpaphp_register_slot()
Andrew Morton wrote:
> On Mon, 7 Apr 2008 17:42:55 -0600
> Alex Chiang <achiang@hp.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@800000020000003/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@hp.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@hp.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.
>
No. It didn't help. I had to hack "slot_nr = 0" all the time to boot my
machine.

I was trying to get some ppc expert to review the patch, as Alex was not
comfortable with the fix/hack. Linas is no longer with IBM :(

Thanks,
Badari



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