USB: kill URBs permanently
looking at usb_kill_urb() it seems to me that it is unnecessarily lenient.
In the use case of disconnect() you never want to use the URB again
(for the same device) But leaving urb->reject elevated will make it easier
to avoid races between read/write and disconnect.
Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 47111e8..a7945ab2 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -522,6 +522,7 @@
}
EXPORT_SYMBOL_GPL(usb_unlink_urb);
+static DEFINE_MUTEX(usb_reject_mutex);
/**
* usb_kill_urb - cancel a transfer request and wait for it to finish
* @urb: pointer to URB describing a previously submitted request,
@@ -544,25 +545,68 @@
*/
void usb_kill_urb(struct urb *urb)
{
- static DEFINE_MUTEX(reject_mutex);
-
might_sleep();
if (!(urb && urb->dev && urb->ep))
return;
- mutex_lock(&reject_mutex);
+ mutex_lock(&usb_reject_mutex);
++urb->reject;
- mutex_unlock(&reject_mutex);
+ mutex_unlock(&usb_reject_mutex);
usb_hcd_unlink_urb(urb, -ENOENT);
wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
- mutex_lock(&reject_mutex);
+ mutex_lock(&usb_reject_mutex);
--urb->reject;
- mutex_unlock(&reject_mutex);
+ mutex_unlock(&usb_reject_mutex);
}
EXPORT_SYMBOL_GPL(usb_kill_urb);
/**
+ * usb_poison_urb - reliably kill a transfer and prevent further use of an URB
+ * @urb: pointer to URB describing a previously submitted request,
+ * may be NULL
+ *
+ * This routine cancels an in-progress request. It is guaranteed that
+ * upon return all completion handlers will have finished and the URB
+ * will be totally idle and cannot be reused. These features make
+ * this an ideal way to stop I/O in a disconnect() callback.
+ * If the request has not already finished or been unlinked
+ * the completion handler will see urb->status == -ENOENT.
+ *
+ * After and while the routine runs, attempts to resubmit the URB will fail
+ * with error -EPERM. Thus even if the URB's completion handler always
+ * tries to resubmit, it will not succeed and the URB will become idle.
+ *
+ * This routine may not be used in an interrupt context (such as a bottom
+ * half or a completion handler), or when holding a spinlock, or in other
+ * situations where the caller can't schedule().
+ */
+void usb_poison_urb(struct urb *urb)
+{
+ might_sleep();
+ if (!(urb && urb->dev && urb->ep))
+ return;
+ mutex_lock(&usb_reject_mutex);
+ ++urb->reject;
+ mutex_unlock(&usb_reject_mutex);
+
+ usb_hcd_unlink_urb(urb, -ENOENT);
+ wait_event(usb_kill_urb_queue, atomic_read(&urb->use_count) == 0);
+}
+EXPORT_SYMBOL_GPL(usb_poison_urb);
+
+void usb_unpoison_urb(struct urb *urb)
+{
+ if (!urb)
+ return;
+
+ mutex_lock(&usb_reject_mutex);
+ --urb->reject;
+ mutex_unlock(&usb_reject_mutex);
+}
+EXPORT_SYMBOL_GPL(usb_unpoison_urb);
+
+/**
* usb_kill_anchored_urbs - cancel transfer requests en masse
* @anchor: anchor the requests are bound to
*