Apart from the early exploration done to find a console keyboard during

the boot process, USB devices must be attached or detached from the usb
task thread in order to avoid races with periodical explorations issued
by uhub(4) interrupts.

Respect this rule when detaching root hubs during a suspend/resume cycle
and avoid some hangs due to the aforementioned race.

Tested by Mattieu Baptiste, thanks!

1 files changed, 21 insertions, 15 deletions

diff --git a/sys/dev/usb/usb.c b/sys/dev/usb/usb.c
index ff5c3b3d2a5..2397a2f308f 100644
--- a/sys/dev/usb/usb.c
+++ b/sys/dev/usb/usb.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: usb.c,v 1.96 2014/05/11 16:33:21 mpi Exp $	*/
+/*	$OpenBSD: usb.c,v 1.97 2014/05/28 11:20:55 mpi Exp $	*/
 /*	$NetBSD: usb.c,v 1.77 2003/01/01 00:10:26 thorpej Exp $	*/
 
 /*
@@ -260,11 +260,15 @@ usb_attach_roothub(struct usb_softc *sc)
 void
 usb_detach_roothub(struct usb_softc *sc)
 {
-	/* Make all devices disconnect. */
-	if (sc->sc_port.device != NULL)
-		usb_disconnect_port(&sc->sc_port, (struct device *)sc);
+	/*
+	 * To avoid races with the usb task thread, mark the root hub
+	 * as disconnecting and schedule an exploration task to detach
+	 * it.
+	 */
+	sc->sc_bus->flags |= USB_BUS_DISCONNECTING;
+	usb_needs_explore(sc->sc_bus->root_hub, 0);
 
-	usb_rem_wait_task(sc->sc_bus->root_hub, &sc->sc_explore_task);
+	usb_wait_task(sc->sc_bus->root_hub, &sc->sc_explore_task);
 
 	sc->sc_bus->root_hub = NULL;
 }
@@ -840,7 +844,18 @@ usb_explore(void *v)
 			usb_delay_ms(sc->sc_bus, pwrdly - waited_ms);
 	}
 
-	sc->sc_bus->root_hub->hub->explore(sc->sc_bus->root_hub);
+	if (sc->sc_bus->flags & USB_BUS_DISCONNECTING) {
+		/* Prevent new tasks from being scheduled. */
+		sc->sc_bus->dying = 1;
+
+		/* Make all devices disconnect. */
+		if (sc->sc_port.device != NULL)
+			usb_disconnect_port(&sc->sc_port, (struct device *)sc);
+
+		sc->sc_bus->flags &= ~USB_BUS_DISCONNECTING;
+	} else {
+		sc->sc_bus->root_hub->hub->explore(sc->sc_bus->root_hub);
+	}
 
 	if (sc->sc_bus->flags & USB_BUS_CONFIG_PENDING) {
 		DPRINTF(("%s: %s: first explore done\n", __func__,
@@ -896,7 +911,6 @@ usb_activate(struct device *self, int act)
 
 	switch (act) {
 	case DVACT_QUIESCE:
-		sc->sc_bus->dying = 1;
 		if (sc->sc_bus->root_hub != NULL)
 			usb_detach_roothub(sc);
 		break;
@@ -914,10 +928,6 @@ usb_activate(struct device *self, int act)
 			usb_needs_explore(sc->sc_bus->root_hub, 0);
 		sc->sc_bus->use_polling--;
 		break;
-	case DVACT_DEACTIVATE:
-		rv = config_activate_children(self, act);
-		sc->sc_bus->dying = 1;
-		break;
 	default:
 		rv = config_activate_children(self, act);
 		break;
@@ -930,10 +940,6 @@ usb_detach(struct device *self, int flags)
 {
 	struct usb_softc *sc = (struct usb_softc *)self;
 
-	DPRINTF(("usb_detach: start\n"));
-
-	sc->sc_bus->dying = 1;
-
 	if (sc->sc_bus->root_hub != NULL) {
 		usb_detach_roothub(sc);