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, 7 insertions, 6 deletions

diff --git a/sys/dev/ic/fxp.c b/sys/dev/ic/fxp.c
index ddfe8bc65c7..cab62a62232 100644
--- a/sys/dev/ic/fxp.c
+++ b/sys/dev/ic/fxp.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fxp.c,v 1.126 2015/11/24 15:43:15 mpi Exp $	*/
+/*	$OpenBSD: fxp.c,v 1.127 2015/11/25 03:09:58 dlg Exp $	*/
 /*	$NetBSD: if_fxp.c,v 1.2 1997/06/05 02:01:55 thorpej Exp $	*/
 
 /*
@@ -676,12 +676,12 @@ fxp_start(struct ifnet *ifp)
 	struct mbuf *m0, *m = NULL;
 	int cnt = sc->sc_cbt_cnt, seg;
 
-	if ((ifp->if_flags & (IFF_OACTIVE | IFF_RUNNING)) != IFF_RUNNING)
+	if (!(ifp->if_flags & IFF_RUNNING) || ifq_is_oactive(&ifp->if_snd))
 		return;
 
 	while (1) {
 		if (cnt >= (FXP_NTXCB - 2)) {
-			ifp->if_flags |= IFF_OACTIVE;
+			ifq_set_oactive(&ifp->if_snd);
 			break;
 		}
 
@@ -846,7 +846,7 @@ fxp_intr(void *arg)
 			sc->sc_cbt_cnt = txcnt;
 			/* Did we transmit any packets? */
 			if (sc->sc_cbt_cons != txs)
-				ifp->if_flags &= ~IFF_OACTIVE;
+				ifq_clr_oactive(&ifp->if_snd);
 			ifp->if_timer = sc->sc_cbt_cnt ? 5 : 0;
 			sc->sc_cbt_cons = txs;
 
@@ -1074,7 +1074,8 @@ fxp_stop(struct fxp_softc *sc, int drain, int softonly)
 	 * between panics, and the watchdog timer)
 	 */
 	ifp->if_timer = 0;
-	ifp->if_flags &= ~(IFF_RUNNING | IFF_OACTIVE);
+	ifp->if_flags &= ~IFF_RUNNING;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	if (!softonly)
 		mii_down(&sc->sc_mii);
@@ -1426,7 +1427,7 @@ fxp_init(void *xsc)
 	mii_mediachg(&sc->sc_mii);
 
 	ifp->if_flags |= IFF_RUNNING;
-	ifp->if_flags &= ~IFF_OACTIVE;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	/*
 	 * Request a software generated interrupt that will be used to