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/pci/if_vmx.c b/sys/dev/pci/if_vmx.c
index 85649e58bd0..055cfe184c2 100644
--- a/sys/dev/pci/if_vmx.c
+++ b/sys/dev/pci/if_vmx.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_vmx.c,v 1.39 2015/11/24 15:25:20 mpi Exp $	*/
+/*	$OpenBSD: if_vmx.c,v 1.40 2015/11/25 03:09:59 dlg Exp $	*/
 
 /*
  * Copyright (c) 2013 Tsubai Masanari
@@ -692,9 +692,9 @@ vmxnet3_txintr(struct vmxnet3_softc *sc, struct vmxnet3_txqueue *tq)
 	if (atomic_add_int_nv(&ring->free, free) == NTXDESC)
 		ifp->if_timer = 0;
 
-	if (ISSET(ifp->if_flags, IFF_OACTIVE)) {
+	if (ifq_is_oactive(&ifp->if_snd)) {
 		KERNEL_LOCK();
-		CLR(ifp->if_flags, IFF_OACTIVE);
+		ifq_clr_oactive(&ifp->if_snd);
 		vmxnet3_start(ifp);
 		KERNEL_UNLOCK();
 	}
@@ -923,7 +923,8 @@ vmxnet3_stop(struct ifnet *ifp)
 	struct vmxnet3_softc *sc = ifp->if_softc;
 	int queue;
 
-	ifp->if_flags &= ~(IFF_RUNNING | IFF_OACTIVE);
+	ifp->if_flags &= ~IFF_RUNNING;
+	ifq_clr_oactive(&ifp->if_snd);
 	ifp->if_timer = 0;
 
 	vmxnet3_disable_all_intrs(sc);
@@ -985,7 +986,7 @@ vmxnet3_init(struct vmxnet3_softc *sc)
 	vmxnet3_link_state(sc);
 
 	ifp->if_flags |= IFF_RUNNING;
-	ifp->if_flags &= ~IFF_OACTIVE;
+	ifq_clr_oactive(&ifp->if_snd);
 
 	return 0;
 }
@@ -1048,7 +1049,7 @@ vmxnet3_start(struct ifnet *ifp)
 	u_int free, used;
 	int n;
 
-	if ((ifp->if_flags & (IFF_RUNNING | IFF_OACTIVE)) != IFF_RUNNING)
+	if (!(ifp->if_flags & IFF_RUNNING) || ifq_is_oactive(&ifp->if_snd))
 		return;
 
 	free = ring->free;
@@ -1056,7 +1057,7 @@ vmxnet3_start(struct ifnet *ifp)
 
 	for (;;) {
 		if (used + NTXSEGS > free) {
-			ifp->if_flags |= IFF_OACTIVE;
+			ifq_set_oactive(&ifp->if_snd);
 			break;
 		}