In iwm(4) and iwx(4), prevent attemps to transition towards the same state

in cases where this would result in a redundant or illegal state transition.

jmc@ observed ASSOC -> ASSOC transitions which would result in a hang.
Such transitions are invalid and never intentionally triggered by net80211.
They imply a race between the Rx interrupt handler and the newstate task.

Tested by jmc@ on AX200 for a week and several known issues seem to be fixed.

1 files changed, 9 insertions, 1 deletions

diff --git a/sys/dev/pci/if_iwm.c b/sys/dev/pci/if_iwm.c
index cb75fbf0f19..c8229ae3802 100644
--- a/sys/dev/pci/if_iwm.c
+++ b/sys/dev/pci/if_iwm.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_iwm.c,v 1.368 2021/09/24 19:02:16 stsp Exp $	*/
+/*	$OpenBSD: if_iwm.c,v 1.369 2021/09/30 09:27:47 stsp Exp $	*/
 
 /*
  * Copyright (c) 2014, 2016 genua gmbh <info@genua.de>
@@ -9004,6 +9004,14 @@ iwm_newstate(struct ieee80211com *ic, enum ieee80211_state nstate, int arg)
 	struct iwm_softc *sc = ifp->if_softc;
 	int i;
 
+	/*
+	 * Prevent attemps to transition towards the same state, unless
+	 * we are scanning in which case a SCAN -> SCAN transition
+	 * triggers another scan iteration.
+	 */
+	if (sc->ns_nstate == nstate && nstate != IEEE80211_S_SCAN)
+		return 0;
+
 	if (ic->ic_state == IEEE80211_S_RUN) {
 		timeout_del(&sc->sc_calib_to);
 		iwm_del_task(sc, systq, &sc->ba_task);