On Mon, Sep 9, 2013 at 1:00 AM, Wei Yang <weiyang@xxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Sep 06, 2013 at 05:09:41PM -0600, Bjorn Helgaas wrote:
>>[+cc Kenji, Alex]
>>
>>On Fri, Sep 06, 2013 at 09:45:56AM +0800, Wei Yang wrote:
>>> In __pci_bus_size_bridges() we check whether a pci bus is a root
>>> bus by testing bus->self. As indicated by commit 79af72d7
>>> ("PCI: pci_is_root_bus helper"), bus->self == NULL is not a proper
>>> way to check the pci root bus.
>>>
>>> This patch changes it to pci_is_root_bus() to check whether it is
>>> a root bus.
>>
>>I think this is a good change, even if only on the grounds of
>>consistency.
>>
>>Did you trip over a case where a root bus has bus->self != NULL?
>>I'd like to know more details about the case where:
>>
>> (bus->parent == NULL) && (bus->self != NULL)
>
> I found one case that (bus->self == NULL) and this bus is not root bus.
>
> Not sure, this case will meet your requirement?
I'm definitely interested in that case as well. Can you include a
complete "lspci -vv" output for the case where this happens?
I suspect this happens with SR-IOV when we create "virtual" buses,
i.e., in virtfn_add_bus(). I think maybe I'll update the comment at
pci_is_root_bus() with a note about why we want to use it instead of
testing for "bus->self == NULL".
I think we still have other tree traversal issues related to those
virtual buses, e.g., the ones I mentioned here [1]. But those are a
separate problem.
Bjorn
[1] http://lkml.kernel.org/r/CAErSpo5sFfr=O-Pp=PyaxGauaEajaTr2aK-EQ_rTVUk1zyz8cA@xxxxxxxxxxxxxx
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