Index: usb/ehci.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/ehci.c,v
retrieving revision 1.193
diff -u -p -u -r1.193 ehci.c
--- usb/ehci.c	4 Nov 2012 12:01:55 -0000	1.193
+++ usb/ehci.c	28 Dec 2012 09:14:37 -0000
@@ -3247,7 +3247,9 @@ ehci_timeout_task(void *addr)
 	DPRINTF(("ehci_timeout_task: xfer=%p\n", xfer));
 
 	mutex_enter(&sc->sc_lock);
-	ehci_abort_xfer(xfer, USBD_TIMEOUT);
+	if (!xfer->done) {
+		ehci_abort_xfer(xfer, USBD_TIMEOUT);
+	}
 	mutex_exit(&sc->sc_lock);
 }
 
Index: usb/ohci.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/ohci.c,v
retrieving revision 1.226
diff -u -p -u -r1.226 ohci.c
--- usb/ohci.c	23 Dec 2012 17:00:13 -0000	1.226
+++ usb/ohci.c	28 Dec 2012 09:14:42 -0000
@@ -2024,7 +2024,9 @@ ohci_timeout_task(void *addr)
 	DPRINTF(("ohci_timeout_task: xfer=%p\n", xfer));
 
 	mutex_enter(&sc->sc_lock);
-	ohci_abort_xfer(xfer, USBD_TIMEOUT);
+	if (!xfer->done) {
+		ohci_abort_xfer(xfer, USBD_TIMEOUT);
+	}
 	mutex_exit(&sc->sc_lock);
 }
 
Index: usb/uhci.c
===================================================================
RCS file: /cvsroot/src/sys/dev/usb/uhci.c,v
retrieving revision 1.249
diff -u -p -u -r1.249 uhci.c
--- usb/uhci.c	24 Jun 2012 10:06:34 -0000	1.249
+++ usb/uhci.c	28 Dec 2012 09:14:43 -0000
@@ -1665,7 +1665,9 @@ uhci_timeout_task(void *addr)
 	DPRINTF(("uhci_timeout_task: xfer=%p\n", xfer));
 
 	mutex_enter(&sc->sc_lock);
-	uhci_abort_xfer(xfer, USBD_TIMEOUT);
+	if (!xfer->done) {
+		uhci_abort_xfer(xfer, USBD_TIMEOUT);
+	}
 	mutex_exit(&sc->sc_lock);
 }