replace IFF_OACTIVE manipulation with mpsafe operations.

there are two things shared between the network stack and drivers
in the send path: the send queue and the IFF_OACTIVE flag. the send
queue is now protected by a mutex. this diff makes the oactive
functionality mpsafe too.

IFF_OACTIVE is part of if_flags. there are two problems with that.
firstly, if_flags is a short and we dont have any MI atomic operations
to manipulate a short. secondly, while we could make the IFF_OACTIVE
operates mpsafe, all changes to other flags would have to be made
safe at the same time, otherwise a read-modify-write cycle on their
updates could clobber the oactive change.

instead, this moves the oactive mark into struct ifqueue and provides
an API for changing it. there's ifq_set_oactive, ifq_clr_oactive,
and ifq_is_oactive. these are modelled on ifsq_set_oactive,
ifsq_clr_oactive, and ifsq_is_oactive in dragonflybsd.

this diff includes changes to all the drivers manipulating IFF_OACTIVE
to now use the ifsq_{set,clr_is}_oactive API too.

ok kettenis@ mpi@ jmatthew@ deraadt@

1 files changed, 6 insertions, 5 deletions

diff --git a/sys/dev/ic/malo.c b/sys/dev/ic/malo.c
index caeefbe719b..22f82b1d81a 100644
--- a/sys/dev/ic/malo.c
+++ b/sys/dev/ic/malo.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: malo.c,v 1.110 2015/11/16 10:03:01 mpi Exp $ */
+/*	$OpenBSD: malo.c,v 1.111 2015/11/25 03:09:58 dlg Exp $ */
 
 /*
  * Copyright (c) 2006 Claudio Jeker <claudio@openbsd.org>
@@ -1006,12 +1006,12 @@ malo_start(struct ifnet *ifp)
 
 	DPRINTF(2, "%s: %s\n", sc->sc_dev.dv_xname, __func__);
 
-	if ((ifp->if_flags & (IFF_RUNNING | IFF_OACTIVE)) != IFF_RUNNING)
+	if (!(ifp->if_flags & IFF_RUNNING) || ifq_is_oactive(&ifp->if_snd))
 		return;
 
 	for (;;) {
 		if (sc->sc_txring.queued >= MALO_TX_RING_COUNT - 1) {
-			ifp->if_flags |= IFF_OACTIVE;
+			ifq_set_oactive(&ifp->if_snd);
 			break;
 		}
 
@@ -1065,7 +1065,8 @@ malo_stop(struct malo_softc *sc)
 		malo_ctl_write4(sc, 0x0c18, (1 << 15));
 
 	/* device is not running anymore */
-	ifp->if_flags &= ~(IFF_RUNNING | IFF_OACTIVE);
+	ifp->if_flags &= ~IFF_RUNNING;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	/* change back to initial state */
 	ieee80211_new_state(ic, IEEE80211_S_INIT, -1);
@@ -1369,7 +1370,7 @@ next:
 	}
 
 	sc->sc_tx_timer = 0;
-	ifp->if_flags &= ~IFF_OACTIVE;
+	ifq_clr_oactive(&ifp->if_snd);
 	malo_start(ifp);
 }