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authorAlex Williamson <alex.williamson@redhat.com>2013-06-11 02:40:57 +0400
committerAlex Williamson <alex.williamson@redhat.com>2013-07-25 02:36:41 +0400
commitd24cdbfd28b7e0ffecb1e281d73e73c03a57f734 (patch)
tree5121604d0025974356f09bb0027e018f1be05e03 /drivers/vfio
parentc64019302bbb0b445484d870e674ab34a19a18a1 (diff)
downloadlinux-d24cdbfd28b7e0ffecb1e281d73e73c03a57f734.tar.xz
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>
Diffstat (limited to 'drivers/vfio')
-rw-r--r--drivers/vfio/pci/vfio_pci.c23
1 files changed, 21 insertions, 2 deletions
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index c5179e269df6..cef6002acbd4 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -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);
}