diff --git a/sys/dev/usb/uhub.c b/sys/dev/usb/uhub.c
index 95421ca0eeb1..a4816145a761 100644
--- a/sys/dev/usb/uhub.c
+++ b/sys/dev/usb/uhub.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: uhub.c,v 1.48 2000/12/29 01:24:56 augustss Exp $	*/
+/*	$NetBSD: uhub.c,v 1.49 2001/01/21 19:00:06 augustss Exp $	*/
 /*	$FreeBSD: src/sys/dev/usb/uhub.c,v 1.18 1999/11/17 22:33:43 n_hibma Exp $	*/
 
 /*
@@ -568,7 +568,7 @@ uhub_intr(usbd_xfer_handle xfer, usbd_private_handle addr, usbd_status status)
 	if (status != USBD_NORMAL_COMPLETION)
 		usbd_clear_endpoint_stall_async(sc->sc_ipipe);
 
-	usb_needs_explore(sc->sc_hub->bus);
+	usb_needs_explore(sc->sc_hub);
 }
 
 #if defined(__FreeBSD__)
diff --git a/sys/dev/usb/usb.c b/sys/dev/usb/usb.c
index 9f0f345d4d61..57850976a179 100644
--- a/sys/dev/usb/usb.c
+++ b/sys/dev/usb/usb.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: usb.c,v 1.50 2001/01/21 16:55:11 augustss Exp $	*/
+/*	$NetBSD: usb.c,v 1.51 2001/01/21 19:00:06 augustss Exp $	*/
 
 /*
  * Copyright (c) 1998 The NetBSD Foundation, Inc.
@@ -93,14 +93,17 @@ struct usb_softc {
 	usbd_bus_handle sc_bus;		/* USB controller */
 	struct usbd_port sc_port;	/* dummy port for root hub */
 
+	SIMPLEQ_HEAD(, usb_task) sc_tasks;
 	struct proc    *sc_event_thread;
 
+	struct usb_task sc_exp_task;
+
 	char		sc_dying;
 };
 
 cdev_decl(usb);
 
-Static usbd_status usb_discover(struct usb_softc *);
+Static void	usb_discover(void *);
 Static void	usb_create_event_thread(void *);
 Static void	usb_event_thread(void *);
 
@@ -143,6 +146,10 @@ USB_ATTACH(usb)
 	sc->sc_bus = aux;
 	sc->sc_bus->usbctl = sc;
 	sc->sc_port.power = USB_MAX_POWER;
+	SIMPLEQ_INIT(&sc->sc_tasks);
+
+	sc->sc_exp_task.fun = usb_discover;
+	sc->sc_exp_task.arg = sc;
 
 	usbrev = sc->sc_bus->usbrev;
 	printf(": USB revision %s", usbrev_str[usbrev]);
@@ -221,34 +228,52 @@ usb_create_event_thread(void *arg)
 	}
 }
 
+void
+usb_add_task(usbd_device_handle dev, struct usb_task *task)
+{
+	struct usb_softc *sc = dev->bus->usbctl;
+	int s;
+
+	s = splusb();
+	if (!task->onqueue) {
+		DPRINTFN(2,("usb_add_task: sc=%p task=%p\n", sc, task));
+		SIMPLEQ_INSERT_TAIL(&sc->sc_tasks, task, next);
+		task->onqueue = 1;
+	} else
+		DPRINTFN(3,("usb_add_task: sc=%p task=%p on q\n", sc, task));
+	wakeup(&sc->sc_tasks);
+	splx(s);
+}
+
 void
 usb_event_thread(void *arg)
 {
 	struct usb_softc *sc = arg;
-	int first = 1;
+	struct usb_task *task;
+	int s;
 
 	DPRINTF(("usb_event_thread: start\n"));
 
 	/* Make sure first discover does something. */
 	sc->sc_bus->needs_explore = 1;
+	usb_discover(sc);
+	config_pending_decr();
 
 	while (!sc->sc_dying) {
-#ifdef USB_DEBUG
-		if (usb_noexplore < 2)
-#endif
-		usb_discover(sc);
-		if (first) {
-			config_pending_decr();
-			first = 0;
+		s = splusb();
+		task = SIMPLEQ_FIRST(&sc->sc_tasks);
+		if (task == NULL) {
+			tsleep(&sc->sc_tasks, PWAIT, "usbevt", 0);
+			task = SIMPLEQ_FIRST(&sc->sc_tasks);
 		}
-#ifdef USB_DEBUG
-		(void)tsleep(&sc->sc_bus->needs_explore, PWAIT, "usbevt",
-		    usb_noexplore ? 0 : hz * 60);
-#else
-		(void)tsleep(&sc->sc_bus->needs_explore, PWAIT, "usbevt",
-		    hz * 60);
-#endif
-		DPRINTFN(2,("usb_event_thread: woke up\n"));
+		DPRINTFN(2,("usb_event_thread: woke up task=%p\n", task));
+		if (task != NULL && !sc->sc_dying) {
+			SIMPLEQ_REMOVE_HEAD(&sc->sc_tasks, task, next);
+			task->onqueue = 0;
+			splx(s);
+			task->fun(task->arg);
+		} else
+			splx(s);
 	}
 	sc->sc_event_thread = NULL;
 
@@ -482,9 +507,16 @@ usbpoll(dev_t dev, int events, struct proc *p)
 }
 
 /* Explore device tree from the root. */
-usbd_status
-usb_discover(struct usb_softc *sc)
+Static void
+usb_discover(void *v)
 {
+	struct usb_softc *sc = v;
+
+	DPRINTFN(2,("usb_discover\n"));
+#ifdef USB_DEBUG
+	if (usb_noexplore > 1)
+		return;
+#endif
 	/* 
 	 * We need mutual exclusion while traversing the device tree,
 	 * but this is guaranteed since this function is only called
@@ -494,15 +526,14 @@ usb_discover(struct usb_softc *sc)
 		sc->sc_bus->needs_explore = 0;
 		sc->sc_bus->root_hub->hub->explore(sc->sc_bus->root_hub);
 	}
-
-	return (USBD_NORMAL_COMPLETION);
 }
 
 void
-usb_needs_explore(usbd_bus_handle bus)
+usb_needs_explore(usbd_device_handle dev)
 {
-	bus->needs_explore = 1;
-	wakeup(&bus->needs_explore);
+	DPRINTFN(2,("usb_needs_explore\n"));
+	dev->bus->needs_explore = 1;
+	usb_add_task(dev, &dev->bus->usbctl->sc_exp_task);
 }
 
 /* Called at splusb() */
@@ -628,7 +659,7 @@ usb_detach(device_ptr_t self, int flags)
 
 	/* Kill off event thread. */
 	if (sc->sc_event_thread) {
-		wakeup(&sc->sc_bus->needs_explore);
+		wakeup(&sc->sc_tasks);
 		if (tsleep(sc, PWAIT, "usbdet", hz * 60))
 			printf("%s: event thread didn't die\n",
 			       USBDEVNAME(sc->sc_dev));
diff --git a/sys/dev/usb/usbdi.h b/sys/dev/usb/usbdi.h
index 00212b79f42e..36c3326bb76d 100644
--- a/sys/dev/usb/usbdi.h
+++ b/sys/dev/usb/usbdi.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: usbdi.h,v 1.47 2001/01/21 02:39:53 augustss Exp $	*/
+/*	$NetBSD: usbdi.h,v 1.48 2001/01/21 19:00:06 augustss Exp $	*/
 /*	$FreeBSD: src/sys/dev/usb/usbdi.h,v 1.18 1999/11/17 22:33:49 n_hibma Exp $	*/
 
 /*
@@ -178,6 +178,21 @@ usbd_status usbd_reload_device_desc(usbd_device_handle);
 
 int usbd_ratecheck(struct timeval *last);
 
+/*
+ * The usb_task structs form a queue of things to run in the USB event
+ * thread.  Normally this is just device discovery when a connect/disconnect
+ * has been detected.  But it may also be used by drivers that need to
+ * perform (short) tasks that must have a process context.
+ */
+struct usb_task {
+	SIMPLEQ_ENTRY(usb_task) next;
+	void (*fun)(void *);
+	void *arg;
+	char onqueue;
+};
+
+void usb_add_task(usbd_device_handle dev, struct usb_task *task);
+
 /* NetBSD attachment information */
 
 /* Attach data */
diff --git a/sys/dev/usb/usbdivar.h b/sys/dev/usb/usbdivar.h
index 92767018561f..099d3624b2e6 100644
--- a/sys/dev/usb/usbdivar.h
+++ b/sys/dev/usb/usbdivar.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: usbdivar.h,v 1.62 2001/01/21 02:39:53 augustss Exp $	*/
+/*	$NetBSD: usbdivar.h,v 1.63 2001/01/21 19:00:06 augustss Exp $	*/
 /*	$FreeBSD: src/sys/dev/usb/usbdivar.h,v 1.11 1999/11/17 22:33:51 n_hibma Exp $	*/
 
 /*
@@ -248,7 +248,7 @@ void		usb_transfer_complete(usbd_xfer_handle xfer);
 void		usb_disconnect_port(struct usbd_port *up, device_ptr_t);
 
 /* Routines from usb.c */
-void		usb_needs_explore(usbd_bus_handle);
+void		usb_needs_explore(usbd_device_handle);
 void		usb_schedsoftintr(struct usbd_bus *);
 
 /*