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, 8 insertions, 7 deletions

diff --git a/sys/dev/usb/if_cdce.c b/sys/dev/usb/if_cdce.c
index d8435a28d67..8bc98d8b629 100644
--- a/sys/dev/usb/if_cdce.c
+++ b/sys/dev/usb/if_cdce.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_cdce.c,v 1.67 2015/11/20 03:35:23 dlg Exp $ */
+/*	$OpenBSD: if_cdce.c,v 1.68 2015/11/25 03:10:00 dlg Exp $ */
 
 /*
  * Copyright (c) 1997, 1998, 1999, 2000-2003 Bill Paul <wpaul@windriver.com>
@@ -386,7 +386,7 @@ cdce_start(struct ifnet *ifp)
 	struct cdce_softc	*sc = ifp->if_softc;
 	struct mbuf		*m_head = NULL;
 
-	if (usbd_is_dying(sc->cdce_udev) || (ifp->if_flags & IFF_OACTIVE))
+	if (usbd_is_dying(sc->cdce_udev) || ifq_is_oactive(&ifp->if_snd))
 		return;
 
 	m_head = ifq_deq_begin(&ifp->if_snd);
@@ -395,7 +395,7 @@ cdce_start(struct ifnet *ifp)
 
 	if (cdce_encap(sc, m_head, 0)) {
 		ifq_deq_rollback(&ifp->if_snd, m_head);
-		ifp->if_flags |= IFF_OACTIVE;
+		ifq_set_oactive(&ifp->if_snd);
 		return;
 	}
 
@@ -406,7 +406,7 @@ cdce_start(struct ifnet *ifp)
 		bpf_mtap(ifp->if_bpf, m_head, BPF_DIRECTION_OUT);
 #endif
 
-	ifp->if_flags |= IFF_OACTIVE;
+	ifq_set_oactive(&ifp->if_snd);
 
 	ifp->if_timer = 6;
 }
@@ -453,7 +453,8 @@ cdce_stop(struct cdce_softc *sc)
 	int		 i;
 
 	ifp->if_timer = 0;
-	ifp->if_flags &= ~(IFF_RUNNING | IFF_OACTIVE);
+	ifp->if_flags &= ~IFF_RUNNING;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	if (sc->cdce_bulkin_pipe != NULL) {
 		usbd_abort_pipe(sc->cdce_bulkin_pipe);
@@ -626,7 +627,7 @@ cdce_init(void *xsc)
 	}
 
 	ifp->if_flags |= IFF_RUNNING;
-	ifp->if_flags &= ~IFF_OACTIVE;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	splx(s);
 }
@@ -800,7 +801,7 @@ cdce_txeof(struct usbd_xfer *xfer, void *priv, usbd_status status)
 	s = splnet();
 
 	ifp->if_timer = 0;
-	ifp->if_flags &= ~IFF_OACTIVE;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	if (status != USBD_NORMAL_COMPLETION) {
 		if (status == USBD_NOT_STARTED || status == USBD_CANCELLED) {