Re: PROBLEM: Deadlock in attach_device() in AMD IOMMU driver

[Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>]

Hi Gregor,

On Tue, May 05, 2015 at 10:24:13AM +0100, Gregor Dick wrote:
> The problem occurs when a network driver (sfc.ko, here an internal
> testing version) enables SR-IOV on its device by calling
> pci_enable_sriov(). There are two PFs for this physical device. This
> call in turn results in a call to virtfn_add(), which takes the
> pci_sriov lock for the first function on the bus. The AMD IOMMU driver
> then handles the device-change notification by calling attach_device()
> which in turn calls pci_enable_ats().  This latter function also
> attempts to take the pci_sriov lock (although this time for
> dev->physfn rather than dev->sriov->dev, but these need not be
> distinct).

Do you see a real deadlock or only the lockdep warning? In the code it
looks like virtfn_add() takes the sriov->lock of the physical device
while pci_enable_ats() (when called from there) takes the sriov->lock of
the virtual function. In this case it couldn't deadlock.


	Joerg