if we get dangerously low on clusters during interrupts, we need

to free some for use on the rx rings on network cards.

this modifies m_cluncount to advise callers when we're in such a
situation, and makes them responsible for freeing up the cluster
for allocation by MCLGETI later.

fixes an awesome lockup with sis(4) henning has been experiencing.
this is not the best fix, but it is better than the current situation.

yep deraadt@ tested by henning@

1 files changed, 34 insertions, 24 deletions

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index b36711e74b0..a357f84a976 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uipc_mbuf.c,v 1.130 2009/08/11 11:53:19 deraadt Exp $	*/
+/*	$OpenBSD: uipc_mbuf.c,v 1.131 2009/08/12 14:39:05 dlg Exp $	*/
 /*	$NetBSD: uipc_mbuf.c,v 1.15.4.1 1996/06/13 17:11:44 cgd Exp $	*/
 
 /*
@@ -372,20 +372,26 @@ m_clcount(struct ifnet *ifp, int pi)
 	ifp->if_data.ifi_mclpool[pi].mcl_alive++;
 }
 
-void
-m_cluncount(struct mbuf *m, int all)
+int
+m_cluncount(struct mbuf *m)
 {
-	struct mbuf_ext *me;
+	struct mbuf_ext *me = &m->m_ext;
+	int pi;
 
-	do {
-		me = &m->m_ext;
-		if (((m->m_flags & (M_EXT|M_CLUSTER)) != (M_EXT|M_CLUSTER)) ||
-		    (me->ext_ifp == NULL))
-			continue;
-
-		me->ext_ifp->if_data.ifi_mclpool[me->ext_backend].mcl_alive--;
-		me->ext_ifp = NULL;
-	} while (all && (m = m->m_next));
+	splassert(IPL_NET);
+
+	if (((m->m_flags & (M_EXT|M_CLUSTER)) != (M_EXT|M_CLUSTER)) ||
+	    (me->ext_ifp == NULL))
+		return (0);
+
+	pi = me->ext_backend;
+	me->ext_ifp->if_data.ifi_mclpool[pi].mcl_alive--;
+	me->ext_ifp = NULL;
+
+	if (mclpools[pi].pr_nitems <= mclpools[pi].pr_minitems)
+		return (1);
+
+	return (0);
 }
 
 struct mbuf *
@@ -468,21 +474,25 @@ m_free(struct mbuf *m)
 void
 m_extfree(struct mbuf *m)
 {
+	struct mbuf_ext *me = &m->m_ext;
+	int pi;
+
 	if (MCLISREFERENCED(m)) {
-		m->m_ext.ext_nextref->m_ext.ext_prevref =
-		    m->m_ext.ext_prevref;
-		m->m_ext.ext_prevref->m_ext.ext_nextref =
-		    m->m_ext.ext_nextref;
+		me->ext_nextref->m_ext.ext_prevref = me->ext_prevref;
+		me->ext_prevref->m_ext.ext_nextref = me->ext_nextref;
 	} else if (m->m_flags & M_CLUSTER) {
-		m_cluncount(m, 0);
-		pool_put(&mclpools[m->m_ext.ext_backend],
-		    m->m_ext.ext_buf);
-	} else if (m->m_ext.ext_free)
-		(*(m->m_ext.ext_free))(m->m_ext.ext_buf,
-		    m->m_ext.ext_size, m->m_ext.ext_arg);
+		pi = me->ext_backend;
+		if (me->ext_ifp != NULL) {
+			me->ext_ifp->if_data.ifi_mclpool[pi].mcl_alive--;
+			me->ext_ifp = NULL;
+		}
+		pool_put(&mclpools[pi], me->ext_buf);
+	} else if (me->ext_free)
+		me->ext_free(me->ext_buf, me->ext_size, me->ext_arg);
 	else
 		panic("unknown type of extension buffer");
-	m->m_ext.ext_size = 0;
+
+	me->ext_size = 0;
 	m->m_flags &= ~(M_EXT|M_CLUSTER);
 }