Almost all of usbip assumes that the_controller->lock is acquired
before vdev->priv_lock. The exception is in
vhci_device_unlink_cleanup(), where locks are acquired in the
reverse order. This leads to occasional deadlocks.
Fixing this is a bit fiddly, as the_controller->lock can't be held
when calling usb_hcd_unlink_urb_from_ep() in the middle of the list
traversal. As I can't rule out concurrent callers to this function
(perhaps it is safe?), the code here becomes slightly uglier - when
locks are dropped in the middle so the list may have emptied itself
(not even list_for_each_entry_safe is safe here).
Signed-off-by: Bernard Blackham <b-linux...@largestprime.net>
diff --git a/drivers/staging/usbip/vhci_hcd.c b/drivers/staging/usbip/vhci_hcd.c
index 12a9a5f..dfeb492 100644
--- a/drivers/staging/usbip/vhci_hcd.c
+++ b/drivers/staging/usbip/vhci_hcd.c
@@ -749,6 +749,7 @@ static void vhci_device_unlink_cleanup(struct vhci_device
*vdev)
{
struct vhci_unlink *unlink, *tmp;
+ spin_lock(&the_controller->lock);
spin_lock(&vdev->priv_lock);
list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
@@ -757,9 +758,12 @@ static void vhci_device_unlink_cleanup(struct vhci_device
*vdev)
kfree(unlink);
}
- list_for_each_entry_safe(unlink, tmp, &vdev->unlink_rx, list) {
+ while (!list_empty(&vdev->unlink_rx)) {
struct urb *urb;
+ unlink = list_first_entry(&vdev->unlink_rx, struct vhci_unlink,
+ list);
+
/* give back URB of unanswered unlink request */
pr_info("unlink cleanup rx %lu\n", unlink->unlink_seqnum);
@@ -774,18 +778,24 @@ static void vhci_device_unlink_cleanup(struct vhci_device
*vdev)
urb->status = -ENODEV;
- spin_lock(&the_controller->lock);
usb_hcd_unlink_urb_from_ep(vhci_to_hcd(the_controller), urb);
+
+ list_del(&unlink->list);
+
+ spin_unlock(&vdev->priv_lock);
spin_unlock(&the_controller->lock);
usb_hcd_giveback_urb(vhci_to_hcd(the_controller), urb,
urb->status);
- list_del(&unlink->list);
+ spin_lock(&the_controller->lock);
+ spin_lock(&vdev->priv_lock);
+
kfree(unlink);
}
spin_unlock(&vdev->priv_lock);
+ spin_unlock(&the_controller->lock);
}
/*
--
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