PERFORCE change 38551 for review

[Sam Leffler]

http://perforce.freebsd.org/chv.cgi?CH=38551

Change 38551 by sam at sam_ebb on 2003/09/24 18:10:56

	Try yet again to deal with timing out nodes.  We cannot hold
	the node lock while sending a management frame as this will
	potentially result in a LOR with a driver lock.  This doesn't
	happen for the Atheros driver but does for the wi driver.
	Use a generation number to help process each node once when
	scanning the node table and drop the node lock if we need to
	timeout a node and send a frame.

Affected files ...

.. //depot/projects/netperf/sys/net80211/ieee80211_node.c#9 edit
.. //depot/projects/netperf/sys/net80211/ieee80211_node.h#6 edit
.. //depot/projects/netperf/sys/net80211/ieee80211_var.h#6 edit

Differences ...

==== //depot/projects/netperf/sys/net80211/ieee80211_node.c#9 (text+ko) ====

@@ -92,6 +92,7 @@
 	ic->ic_node_free = ieee80211_node_free;
 	ic->ic_node_copy = ieee80211_node_copy;
 	ic->ic_node_getrssi = ieee80211_node_getrssi;
+	ic->ic_scangen = 1;
 }
 
 void
@@ -544,30 +545,48 @@
 	mtx_unlock(&ic->ic_nodelock);
 }
 
+/*
+ * Timeout inactive nodes.  Note that we cannot hold the node
+ * lock while sending a frame as this would lead to a LOR.
+ * Instead we use a generation number to mark nodes that we've
+ * scanned and drop the lock and restart a scan if we have to
+ * time out a node.  Since we are single-threaded by virtue of
+ * controlling the inactivity timer we can be sure this will
+ * process each node only once.
+ */
 void
 ieee80211_timeout_nodes(struct ieee80211com *ic)
 {
-	struct ieee80211_node *ni, *nextbs;
+	struct ieee80211_node *ni;
+	u_int gen = ic->ic_scangen++;		/* NB: ok 'cuz single-threaded*/
 
+restart:
 	mtx_lock(&ic->ic_nodelock);
-	for (ni = TAILQ_FIRST(&ic->ic_node); ni != NULL;) {
+	TAILQ_FOREACH(ni, &ic->ic_node, ni_list) {
+		if (ni->ni_scangen == gen)	/* previously handled */
+			continue;
+		ni->ni_scangen = gen;
 		if (++ni->ni_inact > IEEE80211_INACT_MAX) {
 			IEEE80211_DPRINTF(("station %s timed out "
 			    "due to inactivity (%u secs)\n",
 			    ether_sprintf(ni->ni_macaddr),
 			    ni->ni_inact));
-			nextbs = TAILQ_NEXT(ni, ni_list);
 			/*
 			 * Send a deauthenticate frame.
+			 *
+			 * Drop the node lock before sending the
+			 * deauthentication frame in case the driver takes     
+			 * a lock, as this will result in a LOR between the     
+			 * node lock and the driver lock.
 			 */
+			mtx_unlock(&ic->ic_nodelock);
 			IEEE80211_SEND_MGMT(ic, ni,
 			    IEEE80211_FC0_SUBTYPE_DEAUTH,
 			    IEEE80211_REASON_AUTH_EXPIRE);
 			ieee80211_free_node(ic, ni);
 			ic->ic_stats.is_node_timeout++;
-			ni = nextbs;
-		} else
-			ni = TAILQ_NEXT(ni, ni_list);
+			goto restart;
+		}
 	}
 	if (!TAILQ_EMPTY(&ic->ic_node))
 		ic->ic_inact_timer = IEEE80211_INACT_WAIT;

==== //depot/projects/netperf/sys/net80211/ieee80211_node.h#6 (text+ko) ====

@@ -62,6 +62,7 @@
 	TAILQ_ENTRY(ieee80211_node)	ni_list;
 	LIST_ENTRY(ieee80211_node)	ni_hash;
 	u_int			ni_refcnt;
+	u_int			ni_scangen;	/* gen# for timeout scan */
 
 	/* hardware */
 	u_int32_t		ni_rstamp;	/* recv timestamp */

==== //depot/projects/netperf/sys/net80211/ieee80211_var.h#6 (text+ko) ====

@@ -166,6 +166,7 @@
 	u_int16_t		ic_rtsthreshold;
 	u_int16_t		ic_fragthreshold;
 	struct mtx		ic_nodelock;	/* on node table */
+	u_int			ic_scangen;	/* gen# for timeout scan */
 	struct ieee80211_node	*(*ic_node_alloc)(struct ieee80211com *);
 	void			(*ic_node_free)(struct ieee80211com *,
 					struct ieee80211_node *);