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SubjectRe: [PATCH 1/8] pci: Make sriov work with hotplug removal
On 10/18/2011 09:49 AM, Bjorn Helgaas wrote:
> On Mon, Oct 17, 2011 at 4:24 PM, Yinghai Lu<yinghai.lu@oracle.com> wrote:
>> On 10/17/2011 03:12 PM, Bjorn Helgaas wrote:
>>>
>>> Maybe this is the best we can do, but it still doesn't seem ideal, and
>>> it's certainly not obvious when reading the code. It doesn't seem
>>> right for the driver ->remove() method to be calling
>>> pci_destroy_dev(). Won't the core data structures be corrupted if a
>>> defective driver doesn't call pci_disable_sriov()? Seems like we
>>> could end up with a device that's been physically removed, but still
>>> has pci_dev structs hanging around.
>>
>> i did add some print out in
>> pci_stop_bus_device
>> when stop PF, that function is called for those VFs.
>>
>> also driver have to call pci_disable_sriov() and that is current design.
>
> Yep. But I don't have to like the current design :) It doesn't seem
> as robust as it could be.
>
> It took me a long time to puzzle out what was happening here. Here's
> some possible changelog text that would have saved me a lot of time:
>
> The PCI hot-remove path calls pci_stop_bus_devices() via
> pci_remove_bus_device().
>
> pci_stop_bus_devices() traverses the bus->devices list (point A below),
> stopping each device in turn, which calls the driver remove() method. When
> the device is an SR-IOV PF, the driver calls pci_disable_sriov(), which
> also uses pci_remove_bus_device() to remove the VF devices from the
> bus->devices list (point B).
>
> pci_remove_bus_device
> pci_stop_bus_device
> pci_stop_bus_devices(subordinate)
> list_for_each(bus->devices)<-- A
> pci_stop_bus_device(PF)
> ...
> driver->remove
> pci_disable_sriov
> ...
> pci_remove_bus_device(VF)
> <remove from bus_list> <-- B
>
> At B, we're changing the same list we're iterating through at A, so when
> the driver remove() method returns, the pci_stop_bus_devices() iterator has
> a pointer to a list entry that has already been freed.
>
> This patch avoids the problem by building a separate list of all PFs on
> the bus and traversing that at A instead of the bus->devices list.

yes.


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