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vfio-pci: Avoid deadlock on remove 

If an attempt is made to unbind a device from vfio-pci while that
device is in use, the request is blocked until the device becomes
unused.  Unfortunately, that unbind path still grabs the device_lock,
which certain things like __pci_reset_function() also want to take.
This means we need to try to acquire the locks ourselves and use the
pre-locked version, __pci_reset_function_locked().

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Alex Williamson 2013-06-10 16:40:57 -06:00
parent c64019302b
commit d24cdbfd28
1 changed files with 21 additions and 2 deletions
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23
drivers/vfio/pci/vfio_pci.c
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@ -137,8 +137,27 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev)
*/
pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);
if (vdev->reset_works)
__pci_reset_function(pdev);
/*
* Careful, device_lock may already be held. This is the case if
* a driver unbind is blocked. Try to get the locks ourselves to
* prevent a deadlock.
*/
if (vdev->reset_works) {
bool reset_done = false;
if (pci_cfg_access_trylock(pdev)) {
if (device_trylock(&pdev->dev)) {
__pci_reset_function_locked(pdev);
reset_done = true;
device_unlock(&pdev->dev);
}
pci_cfg_access_unlock(pdev);
}
if (!reset_done)
pr_warn("%s: Unable to acquire locks for reset of %s\n",
__func__, dev_name(&pdev->dev));
}
pci_restore_state(pdev);
}