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>
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index c5179e2..cef6002 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -137,8 +137,27 @@
*/
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);
}