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    SubjectRe: [PATCH v5] Fixes to Xen pciback for 3.17.
    On Mon, Jul 14, 2014 at 10:40:42AM -0700, Greg KH wrote:
    > On Mon, Jul 14, 2014 at 12:18:50PM -0400, Konrad Rzeszutek Wilk wrote:
    > > Greg: goto GHK
    > >
    > > This is v5 version of patches to fix some issues in Xen PCIback.
    > >
    > > One of the issues Xen PCI back has that patch:
    > >
    > > is fixing is that a deadlock can happen if the PCI device is
    > > assigned to a guest and we try to 'unbind' it from Xen 'pciback' driver.
    > > The issue is rather simple - the SysFS mechanism for the 'unbind' path
    > > takes a device lock and the code in Xen PCI uses the pci_reset_function
    > > which also takes the same lock. Solution is to use the lock-less version
    > > and mandate that callers of said function in Xen pciback take the lock.
    > > Easy enough.
    > >
    > > GHK:
    > > To guard against this happening in the future we also add an assert in the
    > > form of lockdep assertion. That is OK except that it looks ugly as we take
    > > it straight from the 'struct device' instead of using an appropriate macro.
    > > See:
    > >
    > > + lockdep_assert_held(&dev->dev.mutex);
    > >
    > > (in [PATCH v5 2/6] xen/pciback: Don't deadlock when unbinding).
    > >
    > > The patch: [PATCH v5 3/6] driver core: Provide an wrapper around the mutex
    > > to do.
    > >
    > > introduces a nice wrapper so it is bit cleaner. Greg, if you are OK with
    > > it could you kindly Ack it as I would prefer to put this patchset
    > > via the Xen tree. It would look now as:
    > >
    > > - lockdep_assert_held(&dev->dev.mutex);
    > > + device_lock_assert(&dev->dev);
    > >
    > > I can also squash it in "[PATCH v5 2/6] xen/pciback: Don't deadlock when
    > > unbinding." but since that one is going through the stable tree I wasn't
    > > sure whether you (Greg KH) would be OK with that.
    >
    > You have my ack now, and feel free to squash it into patch 2/6 if you
    > want, I don't mind having that in the stable trees.

    Fantastic! Thank you.
    >
    > thanks,
    >
    > greg k-h


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