Lock down netnatm and mark as MPSAFE:

- Introduce a subsystem mutex, natm_mtx, manipulated with accessor macros
  NATM_LOCK_INIT(), NATM_LOCK(), NATM_UNLOCK(), NATM_LOCK_ASSERT().  It
  protects the consistency of pcb-related data structures.  Finer grained
  locking is possible, but should be done in the context of specific
  measurements (as very little work is done in netnatm -- most is in the
  ATM device driver or socket layer, so there's probably not much
  contention).

- Remove GIANT_REQUIRED, mark as NETISR_MPSAFE, remove
  NET_NEEDS_GIANT("netnatm").

- Conditionally acquire Giant when entering network interfaces for
  ifp->if_ioctl() using IFF_LOCKGIANT(ifp)/IFF_UNLOCKGIANT(ifp) in order
  to coexist with non-MPSAFE atm ifnet drivers..

- De-spl.

MFC after:	2 weeks
Reviewed by:	harti, bms (various versions)

1 files changed, 9 insertions, 6 deletions

diff --git a/sys/net/if_atmsubr.c b/sys/net/if_atmsubr.c
index 1350f5a..07df91c 100644
--- a/sys/net/if_atmsubr.c
+++ b/sys/net/if_atmsubr.c
@@ -256,9 +256,6 @@ atm_input(struct ifnet *ifp, struct atm_pseudohdr *ah, struct mbuf *m,
 {
 	int isr;
 	u_int16_t etype = ETHERTYPE_IP;		/* default */
-#ifdef NATM
-	int s;
-#endif
 
 	if ((ifp->if_flags & IFF_UP) == 0) {
 		m_freem(m);
@@ -284,13 +281,19 @@ atm_input(struct ifnet *ifp, struct atm_pseudohdr *ah, struct mbuf *m,
 
 	if (rxhand) {
 #ifdef NATM
-		struct natmpcb *npcb = rxhand;
+		struct natmpcb *npcb;
 
-		s = splimp();		/* in case 2 atm cards @ diff lvls */
+		/*
+		 * XXXRW: this use of 'rxhand' is not a very good idea, and
+		 * was subject to races even before SMPng due to the release
+		 * of spl here.
+		 */
+		NATM_LOCK();
+		npcb = rxhand;
 		npcb->npcb_inq++;	/* count # in queue */
-		splx(s);
 		isr = NETISR_NATM;
 		m->m_pkthdr.rcvif = rxhand; /* XXX: overload */
+		NATM_UNLOCK();
 #else
 		printf("atm_input: NATM detected but not "
 		    "configured in kernel\n");