Merged revisions 56277 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
r56277 | russell | 2007-02-22 17:08:36 -0600 (Thu, 22 Feb 2007) | 18 lines

Merge changes from team/russell/sla_updates.

This batch of changes to the SLA code does a few different things.

* I made the SLA code event driven instead of having to act in a lot of busy
  loops while dialing things to wait for state changes.  This makes the code
  more efficient and readable at the same time.

* I have implemented a couple of new features.  The first is inbound trunk
  ringing timeouts.  This is an option that defines how long to let an incoming
  call on a trunk to ring.

* I have also implemented ring timeouts for stations.  They may be specified
  for the entire station, meaning it is how long to let the station ring before
  giving up.  You can also specify a ring timeout for a specific trunk on a
  station.  So, you can say that you only want a specific station to ring 5
  seconds if it is line1 ringing, but otherwise, there is no timeout.

........


git-svn-id: http://svn.digium.com/svn/asterisk/trunk@56278 f38db490-d61c-443f-a65b-d21fe96a405b

4 files changed, 688 insertions, 302 deletions

diff --git a/apps/app_meetme.c b/apps/app_meetme.c
index 82d576dc1..5fdb9a13d 100644
--- a/apps/app_meetme.c
+++ b/apps/app_meetme.c
@@ -1,10 +1,13 @@
 /*
  * Asterisk -- An open source telephony toolkit.
  *
- * Copyright (C) 1999 - 2006, Digium, Inc.
+ * Copyright (C) 1999 - 2007, Digium, Inc.
  *
  * Mark Spencer <markster@digium.com>
  *
+ * SLA Implementation by:
+ * Russell Bryant <russell@digium.com>
+ *
  * See http://www.asterisk.org for more information about
  * the Asterisk project. Please do not directly contact
  * any of the maintainers of this project for assistance;
@@ -18,9 +21,10 @@
 
 /*! \file
  *
- * \brief Meet me conference bridge
+ * \brief Meet me conference bridge and Shared Line Appearances
  *
  * \author Mark Spencer <markster@digium.com>
+ * \author (SLA) Russell Bryant <russell@digium.com>
  * 
  * \ingroup applications
  */
@@ -346,6 +350,11 @@ struct ast_conf_user {
 	AST_LIST_ENTRY(ast_conf_user) list;
 };
 
+enum sla_which_trunk_refs {
+	ALL_TRUNK_REFS,
+	INACTIVE_TRUNK_REFS,
+};
+
 enum sla_trunk_state {
 	SLA_TRUNK_STATE_IDLE,
 	SLA_TRUNK_STATE_RINGING,
@@ -364,6 +373,10 @@ struct sla_station {
 	);
 	AST_LIST_HEAD_NOLOCK(, sla_trunk_ref) trunks;
 	struct ast_dial *dial;
+	/*! Ring timeout for this station, for any trunk.  If a ring timeout
+	 *  is set for a specific trunk on this station, that will take
+	 *  priority over this value. */
+	unsigned int ring_timeout;
 };
 
 struct sla_station_ref {
@@ -386,7 +399,10 @@ struct sla_trunk {
 	/*! Number of stations that have this trunk on hold. */
 	unsigned int hold_stations;
 	struct ast_channel *chan;
-	pthread_t station_thread;
+	/*! Ring timeout to use when this trunk is ringing on this specific
+	 *  station.  This takes higher priority than a ring timeout set at
+	 *  the station level. */
+	unsigned int ring_timeout;
 };
 
 struct sla_trunk_ref {
@@ -394,6 +410,7 @@ struct sla_trunk_ref {
 	struct sla_trunk *trunk;
 	enum sla_trunk_state state;
 	struct ast_channel *chan;
+	unsigned int ring_timeout;
 };
 
 static AST_RWLIST_HEAD_STATIC(sla_stations, sla_station);
@@ -401,9 +418,16 @@ static AST_RWLIST_HEAD_STATIC(sla_trunks, sla_trunk);
 
 static const char sla_registrar[] = "SLA";
 
+/*! \brief Event types that can be queued up for the SLA thread */
 enum sla_event_type {
+	/*! A station has put the call on hold */
 	SLA_EVENT_HOLD,
-	SLA_EVENT_UNHOLD
+	/*! A station has taken the call off of hold */
+	SLA_EVENT_UNHOLD,
+	/*! The state of a dial has changed */
+	SLA_EVENT_DIAL_STATE,
+	/*! The state of a ringing trunk has changed */
+	SLA_EVENT_RINGING_TRUNK,
 };
 
 struct sla_event {
@@ -413,6 +437,36 @@ struct sla_event {
 	AST_LIST_ENTRY(sla_event) entry;
 };
 
+/*! \brief A station that failed to be dialed 
+ * \note Only used by the SLA thread. */
+struct sla_failed_station {
+	struct sla_station *station;
+	struct timeval last_try;
+	AST_LIST_ENTRY(sla_failed_station) entry;
+};
+
+/*! \brief A trunk that is ringing */
+struct sla_ringing_trunk {
+	struct sla_trunk *trunk;
+	/*! The time that this trunk started ringing */
+	struct timeval ring_begin;
+	AST_LIST_HEAD_NOLOCK(, sla_station_ref) timed_out_stations;
+	AST_LIST_ENTRY(sla_ringing_trunk) entry;
+};
+
+enum sla_station_hangup {
+	SLA_STATION_HANGUP_NORMAL,
+	SLA_STATION_HANGUP_TIMEOUT,
+};
+
+/*! \brief A station that is ringing */
+struct sla_ringing_station {
+	struct sla_station *station;
+	/*! The time that this station started ringing */
+	struct timeval ring_begin;
+	AST_LIST_ENTRY(sla_ringing_station) entry;
+};
+
 /*!
  * \brief A structure for data used by the sla thread
  */
@@ -421,7 +475,9 @@ static struct sla {
 	pthread_t thread;
 	ast_cond_t cond;
 	ast_mutex_t lock;
-	AST_LIST_HEAD_NOLOCK(, sla_trunk_ref) ringing_trunks;
+	AST_LIST_HEAD_NOLOCK(, sla_ringing_trunk) ringing_trunks;
+	AST_LIST_HEAD_NOLOCK(, sla_ringing_station) ringing_stations;
+	AST_LIST_HEAD_NOLOCK(, sla_failed_station) failed_stations;
 	AST_LIST_HEAD_NOLOCK(, sla_event) event_q;
 	unsigned int stop:1;
 } sla = {
@@ -929,25 +985,33 @@ static int sla_show_trunks(int fd, int argc, char **argv)
 {
 	const struct sla_trunk *trunk;
 
-	ast_cli(fd, "--- Configured SLA Trunks -----------------------------------\n"
-	            "-------------------------------------------------------------\n\n");
+	ast_cli(fd, "\n"
+	            "--- Configured SLA Trunks -----------------------------------\n"
+	            "-------------------------------------------------------------\n"
+	            "---\n");
 	AST_RWLIST_RDLOCK(&sla_trunks);
 	AST_RWLIST_TRAVERSE(&sla_trunks, trunk, entry) {
 		struct sla_station_ref *station_ref;
+		char ring_timeout[16] = "(none)";
+		if (trunk->ring_timeout)
+			snprintf(ring_timeout, sizeof(ring_timeout), "%u Seconds", trunk->ring_timeout);
 		ast_cli(fd, "--- Trunk Name:      %s\n"
 		            "--- ==> Device:      %s\n"
 					"--- ==> AutoContext: %s\n"
+					"--- ==> RingTimeout: %s\n"
 					"--- ==> Stations ...\n",
 					trunk->name, trunk->device, 
-					S_OR(trunk->autocontext, "(none)"));
+					S_OR(trunk->autocontext, "(none)"), 
+					ring_timeout);
 		AST_RWLIST_RDLOCK(&sla_stations);
 		AST_LIST_TRAVERSE(&trunk->stations, station_ref, entry)
-			ast_cli(fd, "--- =====> Station name: %s\n", station_ref->station->name);
+			ast_cli(fd, "---    ==> Station name: %s\n", station_ref->station->name);
 		AST_RWLIST_UNLOCK(&sla_stations);
-		ast_cli(fd, "\n");
+		ast_cli(fd, "---\n");
 	}
 	AST_RWLIST_UNLOCK(&sla_trunks);
-	ast_cli(fd, "-------------------------------------------------------------\n");
+	ast_cli(fd, "-------------------------------------------------------------\n"
+	            "\n");
 
 	return RESULT_SUCCESS;
 }
@@ -973,26 +1037,44 @@ static int sla_show_stations(int fd, int argc, char **argv)
 {
 	const struct sla_station *station;
 
-	ast_cli(fd, "--- Configured SLA Stations ---------------------------------\n"
-	            "-------------------------------------------------------------\n\n");
+	ast_cli(fd, "\n" 
+	            "--- Configured SLA Stations ---------------------------------\n"
+	            "-------------------------------------------------------------\n"
+	            "---\n");
 	AST_RWLIST_RDLOCK(&sla_stations);
 	AST_RWLIST_TRAVERSE(&sla_stations, station, entry) {
 		struct sla_trunk_ref *trunk_ref;
+		char ring_timeout[16] = "(none)";
+		if (station->ring_timeout) {
+			snprintf(ring_timeout, sizeof(ring_timeout), 
+				"%u", station->ring_timeout);
+		}
 		ast_cli(fd, "--- Station Name:    %s\n"
 		            "--- ==> Device:      %s\n"
 					"--- ==> AutoContext: %s\n"
+					"--- ==> RingTimeout: %s\n"
 					"--- ==> Trunks ...\n",
-					station->name, station->device, 
-					S_OR(station->autocontext, "(none)"));
+					station->name, station->device,
+					S_OR(station->autocontext, "(none)"), ring_timeout);
 		AST_RWLIST_RDLOCK(&sla_trunks);
-		AST_LIST_TRAVERSE(&station->trunks, trunk_ref, entry)
-			ast_cli(fd, "--- =====> Trunk Name: %s State: %s\n", 
-				trunk_ref->trunk->name, trunkstate2str(trunk_ref->state));
+		AST_LIST_TRAVERSE(&station->trunks, trunk_ref, entry) {
+			if (trunk_ref->ring_timeout) {
+				snprintf(ring_timeout, sizeof(ring_timeout),
+					"%u", trunk_ref->ring_timeout);
+			} else
+				strcpy(ring_timeout, "(none)");
+			ast_cli(fd, "---    ==> Trunk Name: %s\n", 
+				trunk_ref->trunk->name);
+			ast_cli(fd, "---       ==> State:       %s\n", 
+				trunkstate2str(trunk_ref->state));
+			ast_cli(fd, "---       ==> RingTimeout: %s\n", ring_timeout);
+		}
 		AST_RWLIST_UNLOCK(&sla_trunks);
-		ast_cli(fd, "\n");
+		ast_cli(fd, "---\n");
 	}
 	AST_RWLIST_UNLOCK(&sla_stations);
-	ast_cli(fd, "-------------------------------------------------------------\n");
+	ast_cli(fd, "-------------------------------------------------------------\n"
+	            "\n");
 
 	return RESULT_SUCCESS;
 }
@@ -1100,10 +1182,43 @@ static void conf_queue_dtmf(const struct ast_conference *conf,
 	}
 }
 
-static void sla_queue_event(enum sla_event_type type, const struct ast_channel *chan,
-	struct ast_conference *conf)
+static void sla_queue_event_full(enum sla_event_type type, 
+	struct sla_trunk_ref *trunk_ref, struct sla_station *station, int lock)
 {
 	struct sla_event *event;
+
+	if (!(event = ast_calloc(1, sizeof(*event))))
+		return;
+
+	event->type = type;
+	event->trunk_ref = trunk_ref;
+	event->station = station;
+
+	if (!lock) {
+		AST_LIST_INSERT_TAIL(&sla.event_q, event, entry);
+		return;
+	}
+
+	ast_mutex_lock(&sla.lock);
+	AST_LIST_INSERT_TAIL(&sla.event_q, event, entry);
+	ast_cond_signal(&sla.cond);
+	ast_mutex_unlock(&sla.lock);
+}
+
+static void sla_queue_event_nolock(enum sla_event_type type)
+{
+	sla_queue_event_full(type, NULL, NULL, 0);
+}
+
+static void sla_queue_event(enum sla_event_type type)
+{
+	sla_queue_event_full(type, NULL, NULL, 1);
+}
+
+/*! \brief Queue a SLA event from the conference */
+static void sla_queue_event_conf(enum sla_event_type type, const struct ast_channel *chan,
+	struct ast_conference *conf)
+{
 	struct sla_station *station;
 	struct sla_trunk_ref *trunk_ref = NULL;
 	char *trunk_name;
@@ -1131,17 +1246,7 @@ static void sla_queue_event(enum sla_event_type type, const struct ast_channel *
 		return;
 	}
 
-	if (!(event = ast_calloc(1, sizeof(*event))))
-		return;
-
-	event->type = type;
-	event->trunk_ref = trunk_ref;
-	event->station = station;
-
-	ast_mutex_lock(&sla.lock);
-	AST_LIST_INSERT_TAIL(&sla.event_q, event, entry);
-	ast_cond_signal(&sla.cond);
-	ast_mutex_unlock(&sla.lock);
+	sla_queue_event_full(type, trunk_ref, station, 1);
 }
 
 /* Decrement reference counts, as incremented by find_conf() */
@@ -1936,12 +2041,10 @@ static int conf_run(struct ast_channel *chan, struct ast_conference *conf, int c
 				} else if ((confflags & CONFFLAG_SLA_STATION) && f->frametype == AST_FRAME_CONTROL) {
 					switch (f->subclass) {
 					case AST_CONTROL_HOLD:
-						ast_log(LOG_DEBUG, "Got a HOLD frame!\n");
-						sla_queue_event(SLA_EVENT_HOLD, chan, conf);
+						sla_queue_event_conf(SLA_EVENT_HOLD, chan, conf);
 						break;
 					case AST_CONTROL_UNHOLD:
-						ast_log(LOG_DEBUG, "Got a UNHOLD frame!\n");
-						sla_queue_event(SLA_EVENT_UNHOLD, chan, conf);
+						sla_queue_event_conf(SLA_EVENT_UNHOLD, chan, conf);
 					default:
 						break;
 					}
@@ -2916,7 +3019,7 @@ static void load_config_meetme(void)
 /*! \brief Find an SLA trunk by name
  * \note This must be called with the sla_trunks container locked
  */
-static struct sla_trunk *find_trunk(const char *name)
+static struct sla_trunk *sla_find_trunk(const char *name)
 {
 	struct sla_trunk *trunk = NULL;
 
@@ -2931,7 +3034,7 @@ static struct sla_trunk *find_trunk(const char *name)
 /*! \brief Find an SLA station by name
  * \note This must be called with the sla_stations container locked
  */
-static struct sla_station *find_station(const char *name)
+static struct sla_station *sla_find_station(const char *name)
 {
 	struct sla_station *station = NULL;
 
@@ -2943,7 +3046,7 @@ static struct sla_station *find_station(const char *name)
 	return station;
 }
 
-static struct sla_trunk_ref *find_trunk_ref(const struct sla_station *station,
+static struct sla_trunk_ref *sla_sla_find_trunk_ref(const struct sla_station *station,
 	const char *name)
 {
 	struct sla_trunk_ref *trunk_ref = NULL;
@@ -2956,7 +3059,7 @@ static struct sla_trunk_ref *find_trunk_ref(const struct sla_station *station,
 	return trunk_ref;
 }
 
-static struct sla_station_ref *create_station_ref(struct sla_station *station)
+static struct sla_station_ref *sla_create_station_ref(struct sla_station *station)
 {
 	struct sla_station_ref *station_ref;
 
@@ -2968,7 +3071,21 @@ static struct sla_station_ref *create_station_ref(struct sla_station *station)
 	return station_ref;
 }
 
-static void change_trunk_state(const struct sla_trunk *trunk, enum sla_trunk_state state, int inactive_only)
+static struct sla_ringing_station *sla_create_ringing_station(struct sla_station *station)
+{
+	struct sla_ringing_station *ringing_station;
+
+	if (!(ringing_station = ast_calloc(1, sizeof(*ringing_station))))
+		return NULL;
+
+	ringing_station->station = station;
+	ringing_station->ring_begin = ast_tvnow();
+
+	return ringing_station;
+}
+
+static void sla_change_trunk_state(const struct sla_trunk *trunk, enum sla_trunk_state state, 
+	enum sla_which_trunk_refs inactive_only)
 {
 	struct sla_station *station;
 	struct sla_trunk_ref *trunk_ref;
@@ -3026,7 +3143,7 @@ static void *run_station(void *data)
 	if (ast_atomic_dec_and_test((int *) &trunk_ref->trunk->active_stations)) {
 		strncat(conf_name, "|K", sizeof(conf_name) - strlen(conf_name) - 1);
 		admin_exec(NULL, conf_name);
-		change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, 0);
+		sla_change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, ALL_TRUNK_REFS);
 	}
 
 	ast_dial_join(station->dial);
@@ -3036,216 +3153,426 @@ static void *run_station(void *data)
 	return NULL;
 }
 
-static void *sla_thread(void *data)
+static void sla_stop_ringing_trunk(struct sla_ringing_trunk *ringing_trunk)
 {
-	AST_LIST_HEAD_NOLOCK_STATIC(ringing_stations, sla_station_ref);
-	struct sla_failed_station {
-		struct sla_station *station;
-		struct timeval last_try;
-		AST_LIST_ENTRY(sla_failed_station) entry;
-	};
-	AST_LIST_HEAD_NOLOCK_STATIC(failed_stations, sla_failed_station);
+	char buf[80];
 	struct sla_station_ref *station_ref;
-	struct sla_failed_station *failed_station;
 
-	for (; !sla.stop;) {
-		struct sla_trunk_ref *trunk_ref = NULL;
-		struct sla_event *event;
-		enum ast_dial_result dial_res = AST_DIAL_RESULT_TRYING;
+	snprintf(buf, sizeof(buf), "SLA_%s|K", ringing_trunk->trunk->name);
+	admin_exec(NULL, buf);
+	sla_change_trunk_state(ringing_trunk->trunk, SLA_TRUNK_STATE_IDLE, ALL_TRUNK_REFS);
 
-		ast_mutex_lock(&sla.lock);
-		if (AST_LIST_EMPTY(&sla.ringing_trunks) && AST_LIST_EMPTY(&sla.event_q)) {
-			ast_cond_wait(&sla.cond, &sla.lock);
-			if (sla.stop)
-				break;
-			ast_log(LOG_DEBUG, "Ooh, I was woken up!\n");
-		}
+	while ((station_ref = AST_LIST_REMOVE_HEAD(&ringing_trunk->timed_out_stations, entry)))
+		free(station_ref);
 
-		while ((event = AST_LIST_REMOVE_HEAD(&sla.event_q, entry))) {
-			switch (event->type) {
-			case SLA_EVENT_HOLD:
-				ast_log(LOG_DEBUG, "HOLD, station: %s  trunk: %s\n", 
-					event->station->name, event->trunk_ref->trunk->name);
-				ast_atomic_fetchadd_int((int *) &event->trunk_ref->trunk->hold_stations, 1);
-				event->trunk_ref->state = SLA_TRUNK_STATE_ONHOLD;
-				ast_device_state_changed("SLA:%s_%s", 
-					event->station->name, event->trunk_ref->trunk->name);
-				change_trunk_state(event->trunk_ref->trunk, SLA_TRUNK_STATE_ONHOLD, 1);	
-				break;
-			case SLA_EVENT_UNHOLD:
-				ast_log(LOG_DEBUG, "UNHOLD, station: %s  trunk: %s\n", 
-					event->station->name, event->trunk_ref->trunk->name);
-				if (ast_atomic_dec_and_test((int *) &event->trunk_ref->trunk->hold_stations) == 1)
-					change_trunk_state(event->trunk_ref->trunk, SLA_TRUNK_STATE_UP, 0);
-				else {
-					event->trunk_ref->state = SLA_TRUNK_STATE_UP;
-					ast_device_state_changed("SLA:%s_%s",
-						event->station->name, event->trunk_ref->trunk->name);
-				}
+	free(ringing_trunk);
+}
+
+static void sla_stop_ringing_station(struct sla_ringing_station *ringing_station,
+	enum sla_station_hangup hangup)
+{
+	struct sla_ringing_trunk *ringing_trunk;
+	struct sla_trunk_ref *trunk_ref;
+	struct sla_station_ref *station_ref;
+
+	ast_dial_join(ringing_station->station->dial);
+	ast_dial_destroy(ringing_station->station->dial);
+	ringing_station->station->dial = NULL;
+
+	if (hangup == SLA_STATION_HANGUP_NORMAL)
+		goto done;
+
+	/* If the station is being hung up because of a timeout, then add it to the
+	 * list of timed out stations on each of the ringing trunks.  This is so
+	 * that when doing further processing to figure out which stations should be
+	 * ringing, which trunk to answer, determining timeouts, etc., we know which
+	 * ringing trunks we should ignore. */
+	AST_LIST_TRAVERSE(&sla.ringing_trunks, ringing_trunk, entry) {
+		AST_LIST_TRAVERSE(&ringing_station->station->trunks, trunk_ref, entry) {
+			if (ringing_trunk->trunk == trunk_ref->trunk)
 				break;
-			}
-			free(event);
 		}
+		if (!trunk_ref)
+			continue;
+		if (!(station_ref = sla_create_station_ref(ringing_station->station)))
+			continue;
+		AST_LIST_INSERT_TAIL(&ringing_trunk->timed_out_stations, station_ref, entry);
+	}
+
+done:
+	free(ringing_station);
+}
+
+static void sla_dial_state_callback(struct ast_dial *dial)
+{
+	sla_queue_event(SLA_EVENT_DIAL_STATE);
+}
+
+static void sla_handle_dial_state_event(void)
+{
+	struct sla_ringing_station *ringing_station;
+
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_stations, ringing_station, entry) {
+		struct sla_trunk_ref *s_trunk_ref;
+		struct sla_ringing_trunk *ringing_trunk;
+		struct run_station_args args;
+		enum ast_dial_result dial_res;
+		pthread_attr_t attr;
+		pthread_t dont_care;
+		ast_mutex_t cond_lock;
+		ast_cond_t cond;
 
-		/* At this point, we know there are ringing trunks.  So, make sure that every
-		 * station that uses at least one of the ringing trunks, is ringing. */
-		AST_LIST_TRAVERSE(&sla.ringing_trunks, trunk_ref, entry) {
-			AST_LIST_TRAVERSE(&trunk_ref->trunk->stations, station_ref, entry) {
-				char *tech, *tech_data;
-				struct ast_dial *dial;
-				struct sla_station_ref *ringing_ref;
-				struct sla_failed_station *failed_station;
-				/* Did we fail to dial this station earlier?  If so, has it been
- 				 * a minute since we tried? */
-				AST_LIST_TRAVERSE_SAFE_BEGIN(&failed_stations, failed_station, entry) {
-					if (station_ref->station != failed_station->station)
+		switch ((dial_res = ast_dial_state(ringing_station->station->dial))) {
+		case AST_DIAL_RESULT_HANGUP:
+		case AST_DIAL_RESULT_INVALID:
+		case AST_DIAL_RESULT_FAILED:
+		case AST_DIAL_RESULT_TIMEOUT:
+		case AST_DIAL_RESULT_UNANSWERED:
+			AST_LIST_REMOVE_CURRENT(&sla.ringing_stations, entry);
+			sla_stop_ringing_station(ringing_station, SLA_STATION_HANGUP_NORMAL);
+			break;
+		case AST_DIAL_RESULT_ANSWERED:
+			AST_LIST_REMOVE_CURRENT(&sla.ringing_stations, entry);
+			/* Find the appropriate trunk to answer. */
+			AST_LIST_TRAVERSE(&ringing_station->station->trunks, s_trunk_ref, entry) {
+				ast_mutex_lock(&sla.lock);
+				AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_trunks, ringing_trunk, entry) {
+					struct sla_station_ref *station_ref;
+					if (s_trunk_ref->trunk != ringing_trunk->trunk)
 						continue;
-					if (ast_tvdiff_ms(ast_tvnow(), failed_station->last_try) > 1000) {
-						AST_LIST_REMOVE_CURRENT(&failed_stations, entry);
-						free(failed_station);
-						failed_station = NULL;
+					/* This trunk on the station is ringing.  But, make sure this station
+					 * didn't already time out while this trunk was ringing. */
+					AST_LIST_TRAVERSE(&ringing_trunk->timed_out_stations, station_ref, entry) {
+						if (station_ref->station == ringing_station->station)
+							break;
 					}
+					if (station_ref)
+						continue;
+					AST_LIST_REMOVE_CURRENT(&sla.ringing_trunks, entry);
 					break;
 				}
-				if (failed_station)
-					continue;
 				AST_LIST_TRAVERSE_SAFE_END
-				AST_LIST_TRAVERSE(&ringing_stations, ringing_ref, entry) {
-					if (station_ref->station == ringing_ref->station)
-						break;
-				}
-				if (ringing_ref)
-					continue;
-				if (!(dial = ast_dial_create()))
-					continue;
-				tech_data = ast_strdupa(station_ref->station->device);
-				tech = strsep(&tech_data, "/");
-				if (ast_dial_append(dial, tech, tech_data) == -1) {
-					ast_dial_destroy(dial);
-					continue;
-				}
-				if (ast_dial_run(dial, trunk_ref->trunk->chan, 1) != AST_DIAL_RESULT_TRYING) {
-					ast_dial_destroy(dial);
-					if (!(failed_station = ast_calloc(1, sizeof(*failed_station))))
-						continue;
-					failed_station->station = station_ref->station;
-					failed_station->last_try = ast_tvnow();
-					AST_LIST_INSERT_HEAD(&failed_stations, failed_station, entry);
+				ast_mutex_unlock(&sla.lock);
+				if (ringing_trunk)
+					break;
+			}
+			if (!ringing_trunk) {
+				ast_log(LOG_DEBUG, "Found no ringing trunk for station '%s' to answer!\n",
+					ringing_station->station->name);
+				break;
+			}
+			s_trunk_ref->chan = ast_dial_answered(ringing_station->station->dial);
+			ast_answer(ringing_trunk->trunk->chan);
+			sla_change_trunk_state(ringing_trunk->trunk, SLA_TRUNK_STATE_UP, ALL_TRUNK_REFS);
+			args.trunk_ref = s_trunk_ref;
+			args.station = ringing_station->station;
+			args.cond = &cond;
+			args.cond_lock = &cond_lock;
+			free(ringing_trunk);
+			free(ringing_station);
+			ast_mutex_init(&cond_lock);
+			ast_cond_init(&cond, NULL);
+			pthread_attr_init(&attr);
+			pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+			ast_mutex_lock(&cond_lock);
+			ast_pthread_create_background(&dont_care, &attr, run_station, &args);
+			ast_cond_wait(&cond, &cond_lock);
+			ast_mutex_unlock(&cond_lock);
+			ast_mutex_destroy(&cond_lock);
+			ast_cond_destroy(&cond);
+			pthread_attr_destroy(&attr);
+			break;
+		case AST_DIAL_RESULT_TRYING:
+		case AST_DIAL_RESULT_RINGING:
+		case AST_DIAL_RESULT_PROGRESS:
+		case AST_DIAL_RESULT_PROCEEDING:
+			break;
+		}
+		if (dial_res == AST_DIAL_RESULT_ANSWERED) {
+			/* Queue up reprocessing ringing trunks, and then ringing stations again */
+			sla_queue_event(SLA_EVENT_RINGING_TRUNK);
+			sla_queue_event(SLA_EVENT_DIAL_STATE);
+			break;
+		}
+	}
+	AST_LIST_TRAVERSE_SAFE_END
+}
+
+static void sla_handle_ringing_trunk_event(void)
+{
+	struct sla_trunk_ref *trunk_ref;
+	struct sla_station_ref *station_ref;
+	struct sla_ringing_trunk *ringing_trunk;
+	struct sla_ringing_station *ringing_station;
+
+	ast_mutex_lock(&sla.lock);
+
+	/* Make sure that every station that uses at least one of the ringing
+	 * trunks, is ringing. */
+	AST_LIST_TRAVERSE(&sla.ringing_trunks, ringing_trunk, entry) {
+		AST_LIST_TRAVERSE(&ringing_trunk->trunk->stations, station_ref, entry) {
+			char *tech, *tech_data;
+			struct ast_dial *dial;
+			struct sla_failed_station *failed_station;
+			struct sla_station_ref *timed_out_station;
+			/* Did we fail to dial this station earlier?  If so, has it been
+ 			 * a minute since we tried? */
+			AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.failed_stations, failed_station, entry) {
+				if (station_ref->station != failed_station->station)
 					continue;
+				if (ast_tvdiff_ms(ast_tvnow(), failed_station->last_try) > 1000) {
+					AST_LIST_REMOVE_CURRENT(&sla.failed_stations, entry);
+					free(failed_station);
+					failed_station = NULL;
 				}
-				if (!(ringing_ref = create_station_ref(station_ref->station))) {
-					ast_dial_join(dial);
-					ast_dial_destroy(dial);
+				break;
+			}
+			if (failed_station)
+				continue;
+			AST_LIST_TRAVERSE_SAFE_END
+			AST_LIST_TRAVERSE(&sla.ringing_stations, ringing_station, entry) {
+				if (station_ref->station == ringing_station->station)
+					break;
+			}
+			if (ringing_station)
+				continue;
+			/* If this station already timed out while this trunk was ringing,
+			 * do not dial it again for this ringing trunk. */
+			AST_LIST_TRAVERSE(&ringing_trunk->timed_out_stations, timed_out_station, entry) {
+				if (station_ref->station == timed_out_station->station)
+					break;
+			}
+			if (timed_out_station)
+				continue;
+			if (!(dial = ast_dial_create()))
+				continue;
+			ast_dial_set_state_callback(dial, sla_dial_state_callback);
+			tech_data = ast_strdupa(station_ref->station->device);
+			tech = strsep(&tech_data, "/");
+			if (ast_dial_append(dial, tech, tech_data) == -1) {
+				ast_dial_destroy(dial);
+				continue;
+			}
+			if (ast_dial_run(dial, ringing_trunk->trunk->chan, 1) != AST_DIAL_RESULT_TRYING) {
+				ast_dial_destroy(dial);
+				if (!(failed_station = ast_calloc(1, sizeof(*failed_station))))
 					continue;
-				}
-				station_ref->station->dial = dial;
-				AST_LIST_INSERT_HEAD(&ringing_stations, ringing_ref, entry);
-				ast_log(LOG_DEBUG, "Started dialing station '%s'\n", station_ref->station->name);
+				failed_station->station = station_ref->station;
+				failed_station->last_try = ast_tvnow();
+				AST_LIST_INSERT_HEAD(&sla.failed_stations, failed_station, entry);
+				continue;
+			}
+			if (!(ringing_station = sla_create_ringing_station(station_ref->station))) {
+				ast_dial_join(dial);
+				ast_dial_destroy(dial);
+				continue;
 			}
+			station_ref->station->dial = dial;
+			AST_LIST_INSERT_HEAD(&sla.ringing_stations, ringing_station, entry);
+			ast_log(LOG_DEBUG, "Started dialing station '%s'\n", station_ref->station->name);
 		}
-		ast_mutex_unlock(&sla.lock);
-		/* Now, all of the stations that should be ringing, are ringing. */
-		
-		AST_LIST_TRAVERSE_SAFE_BEGIN(&ringing_stations, station_ref, entry) {
-			struct sla_trunk_ref *s_trunk_ref;
-			struct run_station_args args;
-			pthread_attr_t attr;
-			pthread_t dont_care;
-			ast_mutex_t cond_lock;
-			ast_cond_t cond;
-
-			switch ((dial_res = ast_dial_state(station_ref->station->dial))) {
-			case AST_DIAL_RESULT_HANGUP:
-			case AST_DIAL_RESULT_INVALID:
-			case AST_DIAL_RESULT_FAILED:
-			case AST_DIAL_RESULT_TIMEOUT:
-			case AST_DIAL_RESULT_UNANSWERED:
-				AST_LIST_REMOVE_CURRENT(&ringing_stations, entry);
-				ast_dial_join(station_ref->station->dial);
-				ast_dial_destroy(station_ref->station->dial);
-				station_ref->station->dial = NULL;
-				free(station_ref);
-				break;
-			case AST_DIAL_RESULT_ANSWERED:
-				AST_LIST_REMOVE_CURRENT(&ringing_stations, entry);
-				/* Find the appropriate trunk to answer. */
-				AST_LIST_TRAVERSE(&station_ref->station->trunks, s_trunk_ref, entry) {
-					ast_mutex_lock(&sla.lock);
-					AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_trunks, trunk_ref, entry) {
-						if (s_trunk_ref->trunk == trunk_ref->trunk) {
-							AST_LIST_REMOVE_CURRENT(&sla.ringing_trunks, entry);
-							break;
-						}
-					}
-					AST_LIST_TRAVERSE_SAFE_END
-					ast_mutex_unlock(&sla.lock);
-					if (trunk_ref)
-						break;
-				}
-				if (!trunk_ref) {
-					ast_log(LOG_DEBUG, "Found no ringing trunk for station '%s' to answer!\n",
-						station_ref->station->name);
+	}
+	ast_mutex_unlock(&sla.lock);
+	/* Now, all of the stations that should be ringing, are ringing. */
+	
+	/* Find stations that shouldn't be ringing anymore. */
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_stations, ringing_station, entry) {
+		AST_LIST_TRAVERSE(&ringing_station->station->trunks, trunk_ref, entry) {
+			struct sla_ringing_trunk *ringing_trunk;
+			ast_mutex_lock(&sla.lock);
+			AST_LIST_TRAVERSE(&sla.ringing_trunks, ringing_trunk, entry) {
+				if (trunk_ref->trunk == ringing_trunk->trunk)
 					break;
-				}
-				s_trunk_ref->chan = ast_dial_answered(station_ref->station->dial);
-				ast_answer(trunk_ref->trunk->chan);
-				change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_UP, 0);
-				args.trunk_ref = s_trunk_ref;
-				args.station = station_ref->station;
-				args.cond = &cond;
-				args.cond_lock = &cond_lock;
-				free(trunk_ref);
-				free(station_ref);
-				ast_mutex_init(&cond_lock);
-				ast_cond_init(&cond, NULL);
-				pthread_attr_init(&attr);
-				pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-				ast_mutex_lock(&cond_lock);
-				ast_pthread_create_background(&dont_care, &attr, run_station, &args);
-				ast_cond_wait(&cond, &cond_lock);
-				ast_mutex_unlock(&cond_lock);
-				ast_mutex_destroy(&cond_lock);
-				ast_cond_destroy(&cond);
-				pthread_attr_destroy(&attr);
-				break;
-			case AST_DIAL_RESULT_TRYING:
-			case AST_DIAL_RESULT_RINGING:
-			case AST_DIAL_RESULT_PROGRESS:
-			case AST_DIAL_RESULT_PROCEEDING:
-				break;
 			}
-			if (dial_res == AST_DIAL_RESULT_ANSWERED || !AST_LIST_EMPTY(&sla.event_q))
+			ast_mutex_unlock(&sla.lock);
+			if (ringing_trunk)
 				break;
 		}
-		AST_LIST_TRAVERSE_SAFE_END
-		/* Find stations that shouldn't be ringing anymore. */
-		AST_LIST_TRAVERSE_SAFE_BEGIN(&ringing_stations, station_ref, entry) {
-			AST_LIST_TRAVERSE(&station_ref->station->trunks, trunk_ref, entry) {
-				struct sla_trunk_ref *ringing_ref;
-				ast_mutex_lock(&sla.lock);
-				AST_LIST_TRAVERSE(&sla.ringing_trunks, ringing_ref, entry) {
-					if (trunk_ref->trunk == ringing_ref->trunk)
-						break;
-				}
-				ast_mutex_unlock(&sla.lock);
-				if (ringing_ref)
+		if (!trunk_ref) {
+			AST_LIST_REMOVE_CURRENT(&sla.ringing_stations, entry);
+			ast_dial_join(ringing_station->station->dial);
+			ast_dial_destroy(ringing_station->station->dial);
+			ringing_station->station->dial = NULL;
+			free(ringing_station);
+		}
+	}
+	AST_LIST_TRAVERSE_SAFE_END
+}
+
+static void sla_handle_hold_event(struct sla_event *event)
+{
+	ast_atomic_fetchadd_int((int *) &event->trunk_ref->trunk->hold_stations, 1);
+	event->trunk_ref->state = SLA_TRUNK_STATE_ONHOLD;
+	ast_device_state_changed("SLA:%s_%s", 
+		event->station->name, event->trunk_ref->trunk->name);
+	sla_change_trunk_state(event->trunk_ref->trunk, SLA_TRUNK_STATE_ONHOLD, INACTIVE_TRUNK_REFS);	
+}
+
+static void sla_handle_unhold_event(struct sla_event *event)
+{
+	if (ast_atomic_dec_and_test((int *) &event->trunk_ref->trunk->hold_stations) == 1)
+		sla_change_trunk_state(event->trunk_ref->trunk, SLA_TRUNK_STATE_UP, ALL_TRUNK_REFS);
+	else {
+		event->trunk_ref->state = SLA_TRUNK_STATE_UP;
+		ast_device_state_changed("SLA:%s_%s",
+			event->station->name, event->trunk_ref->trunk->name);
+	}
+}
+
+/*! \brief Calculate the time until the next known event
+ *  \note Called with sla.lock locked */
+static int sla_process_timers(struct timespec *ts)
+{
+	struct sla_ringing_trunk *ringing_trunk;
+	struct sla_ringing_station *ringing_station;
+	unsigned int timeout = UINT_MAX;
+	struct timeval tv;
+	unsigned int change_made = 0;
+
+	/* Check for ring timeouts on ringing trunks */
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_trunks, ringing_trunk, entry) {
+		int time_left, time_elapsed;
+		if (!ringing_trunk->trunk->ring_timeout)
+			continue;
+		time_elapsed = ast_tvdiff_ms(ast_tvnow(), ringing_trunk->ring_begin);
+		time_left = (ringing_trunk->trunk->ring_timeout * 1000) - time_elapsed;
+		if (time_left <= 0) {
+			AST_LIST_REMOVE_CURRENT(&sla.ringing_trunks, entry);
+			sla_stop_ringing_trunk(ringing_trunk);
+			change_made = 1;
+			continue;
+		}
+		if (time_left < timeout)
+			timeout = time_left;
+	}
+	AST_LIST_TRAVERSE_SAFE_END
+
+	/* Check for ring timeouts on ringing stations */
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_stations, ringing_station, entry) {
+		unsigned int ring_timeout = 0;
+		int time_elapsed, time_left, final_trunk_time_left = INT_MIN;
+		struct sla_trunk_ref *trunk_ref;
+		/* If there are any ring timeouts specified for a specific trunk
+		 * on the station, then use the highest per-trunk ring timeout.
+		 * Otherwise, use the ring timeout set for the entire station. */
+		AST_LIST_TRAVERSE(&ringing_station->station->trunks, trunk_ref, entry) {
+			struct sla_station_ref *station_ref;
+			int trunk_time_elapsed, trunk_time_left;
+			AST_LIST_TRAVERSE(&sla.ringing_trunks, ringing_trunk, entry) {
+				if (ringing_trunk->trunk == trunk_ref->trunk)
 					break;
 			}
-			if (!trunk_ref) {
-				AST_LIST_REMOVE_CURRENT(&ringing_stations, entry);
-				ast_dial_join(station_ref->station->dial);
-				ast_dial_destroy(station_ref->station->dial);
-				station_ref->station->dial = NULL;
-				free(station_ref);
+			if (!ringing_trunk)
+				continue;
+			/* If there is a trunk that is ringing without a timeout, then the
+			 * only timeout that could matter is a global station ring timeout. */
+			if (!trunk_ref->ring_timeout) {
+				final_trunk_time_left = INT_MAX;
+				break;
 			}
+			/* This trunk on this station is ringing and has a timeout.
+			 * However, make sure this trunk isn't still ringing from a
+			 * previous timeout.  If so, don't consider it. */
+			AST_LIST_TRAVERSE(&ringing_trunk->timed_out_stations, station_ref, entry) {
+				if (station_ref->station == ringing_station->station)
+					break;
+			}
+			if (station_ref)
+				continue;
+			trunk_time_elapsed = ast_tvdiff_ms(ast_tvnow(), ringing_trunk->ring_begin);
+			trunk_time_left = (trunk_ref->ring_timeout * 1000) - trunk_time_elapsed;
+			if (trunk_time_left > final_trunk_time_left)
+				final_trunk_time_left = trunk_time_left;
 		}
-		AST_LIST_TRAVERSE_SAFE_END
+		if (final_trunk_time_left == INT_MAX && !ringing_station->station->ring_timeout)
+			continue;
+
+		ring_timeout = ringing_station->station->ring_timeout;
+		time_elapsed = ast_tvdiff_ms(ast_tvnow(), ringing_station->ring_begin);
+		time_left = (ring_timeout * 1000) - time_elapsed;
+		/* If the time left based on the per-trunk timeouts is smaller than the
+		 * global station ring timeout, use that. */
+		if (final_trunk_time_left > INT_MIN && final_trunk_time_left < time_left)
+			time_left = final_trunk_time_left;
+		if (time_left <= 0) {
+			AST_LIST_REMOVE_CURRENT(&sla.ringing_stations, entry);
+			sla_stop_ringing_station(ringing_station, SLA_STATION_HANGUP_TIMEOUT);
+			change_made = 1;
+			continue;
+		}
+		if (time_left < timeout)
+			timeout = time_left;
 	}
+	AST_LIST_TRAVERSE_SAFE_END
 
-	while ((station_ref = AST_LIST_REMOVE_HEAD(&ringing_stations, entry)))
-		free(station_ref);
+	/* queue reprocessing of ringing trunks */
+	if (change_made)
+		sla_queue_event_nolock(SLA_EVENT_RINGING_TRUNK);
+
+	if (timeout == UINT_MAX)
+		return 0;
+
+	if (ts) {
+		tv = ast_tvadd(ast_tvnow(), ast_samp2tv(timeout, 1000));
+		ts->tv_sec = tv.tv_sec;
+		ts->tv_nsec = tv.tv_usec * 1000;
+	}
+
+	return 1;
+}
+
+static void *sla_thread(void *data)
+{
+	struct sla_failed_station *failed_station;
+	struct sla_ringing_station *ringing_station;
+
+	ast_mutex_lock(&sla.lock);
+
+	while (!sla.stop) {
+		struct sla_event *event;
+		struct timespec ts = { 0, };
+		unsigned int have_timeout = 0;
+
+		if (AST_LIST_EMPTY(&sla.event_q)) {
+			if ((have_timeout = sla_process_timers(&ts)))
+				ast_cond_timedwait(&sla.cond, &sla.lock, &ts);
+			else
+				ast_cond_wait(&sla.cond, &sla.lock);
+			if (sla.stop)
+				break;
+			ast_log(LOG_DEBUG, "Ooh, I was woken up!\n");
+		}
+
+		if (have_timeout)
+			sla_process_timers(NULL);
 
-	while ((failed_station = AST_LIST_REMOVE_HEAD(&failed_stations, entry)))
+		while ((event = AST_LIST_REMOVE_HEAD(&sla.event_q, entry))) {
+			ast_mutex_unlock(&sla.lock);
+			switch (event->type) {
+			case SLA_EVENT_HOLD:
+				sla_handle_hold_event(event);
+				break;
+			case SLA_EVENT_UNHOLD:
+				sla_handle_unhold_event(event);				
+				break;
+			case SLA_EVENT_DIAL_STATE:
+				sla_handle_dial_state_event();
+				break;
+			case SLA_EVENT_RINGING_TRUNK:
+				sla_handle_ringing_trunk_event();
+				break;
+			}
+			free(event);
+			ast_mutex_lock(&sla.lock);
+		}
+	}
+
+	ast_mutex_unlock(&sla.lock);
+
+	while ((ringing_station = AST_LIST_REMOVE_HEAD(&sla.ringing_stations, entry)))
+		free(ringing_station);
+
+	while ((failed_station = AST_LIST_REMOVE_HEAD(&sla.failed_stations, entry)))
 		free(failed_station);
 
 	return NULL;
@@ -3376,7 +3703,7 @@ static int slastation_exec(struct ast_channel *chan, void *data)
 	}
 
 	AST_RWLIST_RDLOCK(&sla_stations);
-	station = find_station(station_name);
+	station = sla_find_station(station_name);
 	AST_RWLIST_UNLOCK(&sla_stations);
 
 	if (!station) {
@@ -3387,7 +3714,7 @@ static int slastation_exec(struct ast_channel *chan, void *data)
 
 	AST_RWLIST_RDLOCK(&sla_trunks);
 	if (!ast_strlen_zero(trunk_name))
-		trunk_ref = find_trunk_ref(station, trunk_name);
+		trunk_ref = sla_sla_find_trunk_ref(station, trunk_name);
 	else {
 		AST_LIST_TRAVERSE(&station->trunks, trunk_ref, entry) {
 			if (trunk_ref->state == SLA_TRUNK_STATE_IDLE)
@@ -3413,7 +3740,7 @@ static int slastation_exec(struct ast_channel *chan, void *data)
 			.cond_lock = &cond_lock,
 			.cond = &cond,
 		};
-		change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_UP, 0);
+		sla_change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_UP, ALL_TRUNK_REFS);
 		/* Create a thread to dial the trunk and dump it into the conference.
 		 * However, we want to wait until the trunk has been dialed and the
 		 * conference is created before continuing on here. */
@@ -3433,7 +3760,7 @@ static int slastation_exec(struct ast_channel *chan, void *data)
 		if (!trunk_ref->trunk->chan) {
 			ast_log(LOG_DEBUG, "Trunk didn't get created. chan: %lx\n", (long) trunk_ref->trunk->chan);
 			pbx_builtin_setvar_helper(chan, "SLASTATION_STATUS", "CONGESTION");
-			change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, 0);
+			sla_change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, ALL_TRUNK_REFS);
 			return 0;
 		}
 	}
@@ -3455,7 +3782,7 @@ static int slastation_exec(struct ast_channel *chan, void *data)
 	if (res == 1) {	
 		strncat(conf_name, "|K", sizeof(conf_name) - strlen(conf_name) - 1);
 		admin_exec(NULL, conf_name);
-		change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, 0);
+		sla_change_trunk_state(trunk_ref->trunk, SLA_TRUNK_STATE_IDLE, ALL_TRUNK_REFS);
 	}
 	
 	pbx_builtin_setvar_helper(chan, "SLASTATION_STATUS", "SUCCESS");
@@ -3475,6 +3802,27 @@ static struct sla_trunk_ref *create_trunk_ref(struct sla_trunk *trunk)
 	return trunk_ref;
 }
 
+static struct sla_ringing_trunk *queue_ringing_trunk(struct sla_trunk *trunk)
+{
+	struct sla_ringing_trunk *ringing_trunk;
+
+	if (!(ringing_trunk = ast_calloc(1, sizeof(*ringing_trunk))))
+		return NULL;
+	
+	ringing_trunk->trunk = trunk;
+	ringing_trunk->ring_begin = ast_tvnow();
+
+	sla_change_trunk_state(trunk, SLA_TRUNK_STATE_RINGING, 0);
+
+	ast_mutex_lock(&sla.lock);
+	AST_LIST_INSERT_HEAD(&sla.ringing_trunks, ringing_trunk, entry);
+	ast_mutex_unlock(&sla.lock);
+
+	sla_queue_event(SLA_EVENT_RINGING_TRUNK);
+
+	return ringing_trunk;
+}
+
 static int slatrunk_exec(struct ast_channel *chan, void *data)
 {
 	const char *trunk_name = data;
@@ -3482,10 +3830,10 @@ static int slatrunk_exec(struct ast_channel *chan, void *data)
 	struct ast_conference *conf;
 	struct ast_flags conf_flags = { 0 };
 	struct sla_trunk *trunk;
-	struct sla_trunk_ref *trunk_ref;
+	struct sla_ringing_trunk *ringing_trunk;
 
 	AST_RWLIST_RDLOCK(&sla_trunks);
-	trunk = find_trunk(trunk_name);
+	trunk = sla_find_trunk(trunk_name);
 	AST_RWLIST_UNLOCK(&sla_trunks);
 	if (!trunk) {
 		ast_log(LOG_ERROR, "SLA Trunk '%s' not found!\n", trunk_name);
@@ -3502,19 +3850,11 @@ static int slatrunk_exec(struct ast_channel *chan, void *data)
 	}
 	trunk->chan = chan;
 
-	if (!(trunk_ref = create_trunk_ref(trunk))) {
+	if (!(ringing_trunk = queue_ringing_trunk(trunk))) {
 		pbx_builtin_setvar_helper(chan, "SLATRUNK_STATUS", "FAILURE");
 		return 0;
 	}
 
-	change_trunk_state(trunk, SLA_TRUNK_STATE_RINGING, 0);
-
-	ast_mutex_lock(&sla.lock);
-	if (AST_LIST_EMPTY(&sla.ringing_trunks))
-		ast_cond_signal(&sla.cond);
-	AST_LIST_INSERT_HEAD(&sla.ringing_trunks, trunk_ref, entry);
-	ast_mutex_unlock(&sla.lock);
-
 	snprintf(conf_name, sizeof(conf_name), "SLA_%s", trunk_name);
 	conf = build_conf(conf_name, "", "", 1, 1, 1);
 	if (!conf) {
@@ -3533,17 +3873,18 @@ static int slatrunk_exec(struct ast_channel *chan, void *data)
 
 	/* Remove the entry from the list of ringing trunks if it is still there. */
 	ast_mutex_lock(&sla.lock);
-	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_trunks, trunk_ref, entry) {
-		if (trunk_ref->trunk == trunk) {
+	AST_LIST_TRAVERSE_SAFE_BEGIN(&sla.ringing_trunks, ringing_trunk, entry) {
+		if (ringing_trunk->trunk == trunk) {
 			AST_LIST_REMOVE_CURRENT(&sla.ringing_trunks, entry);
 			break;
 		}
 	}
 	AST_LIST_TRAVERSE_SAFE_END
 	ast_mutex_unlock(&sla.lock);
-	if (trunk_ref) {
-		free(trunk_ref);
+	if (ringing_trunk) {
+		free(ringing_trunk);
 		pbx_builtin_setvar_helper(chan, "SLATRUNK_STATUS", "UNANSWERED");
+		sla_queue_event(SLA_EVENT_RINGING_TRUNK);
 	}
 
 	return 0;
@@ -3638,7 +3979,7 @@ static void destroy_station(struct sla_station *station)
 	free(station);
 }
 
-static void destroy_sla(void)
+static void sla_destroy(void)
 {
 	struct sla_trunk *trunk;
 	struct sla_station *station;
@@ -3665,7 +4006,7 @@ static void destroy_sla(void)
 	ast_cond_destroy(&sla.cond);
 }
 
-static int check_device(const char *device)
+static int sla_check_device(const char *device)
 {
 	char *tech, *tech_data;
 
@@ -3678,7 +4019,7 @@ static int check_device(const char *device)
 	return 0;
 }
 
-static int build_trunk(struct ast_config *cfg, const char *cat)
+static int sla_build_trunk(struct ast_config *cfg, const char *cat)
 {
 	struct sla_trunk *trunk;
 	struct ast_variable *var;
@@ -3689,7 +4030,7 @@ static int build_trunk(struct ast_config *cfg, const char *cat)
 		return -1;
 	}
 
-	if (check_device(dev)) {
+	if (sla_check_device(dev)) {
 		ast_log(LOG_ERROR, "SLA Trunk '%s' define with invalid device '%s'!\n",
 			cat, dev);
 		return -1;
@@ -3708,7 +4049,13 @@ static int build_trunk(struct ast_config *cfg, const char *cat)
 	for (var = ast_variable_browse(cfg, cat); var; var = var->next) {
 		if (!strcasecmp(var->name, "autocontext"))
 			ast_string_field_set(trunk, autocontext, var->value);
-		else if (strcasecmp(var->name, "type") && strcasecmp(var->name, "device")) {
+		else if (!strcasecmp(var->name, "ringtimeout")) {
+			if (sscanf(var->value, "%u", &trunk->ring_timeout) != 1) {
+				ast_log(LOG_WARNING, "Invalid ringtimeout '%s' specified for trunk '%s'\n",
+					var->value, trunk->name);
+				trunk->ring_timeout = 0;
+			}
+		} else if (strcasecmp(var->name, "type") && strcasecmp(var->name, "device")) {
 			ast_log(LOG_ERROR, "Invalid option '%s' specified at line %d of %s!\n",
 				var->name, var->lineno, SLA_CONFIG_FILE);
 		}
@@ -3733,13 +4080,64 @@ static int build_trunk(struct ast_config *cfg, const char *cat)
 	}
 
 	AST_RWLIST_WRLOCK(&sla_trunks);
-	AST_RWLIST_INSERT_HEAD(&sla_trunks, trunk, entry);
+	AST_RWLIST_INSERT_TAIL(&sla_trunks, trunk, entry);
 	AST_RWLIST_UNLOCK(&sla_trunks);
 
 	return 0;
 }
 
-static int build_station(struct ast_config *cfg, const char *cat)
+static void sla_add_trunk_to_station(struct sla_station *station, struct ast_variable *var)
+{
+	struct sla_trunk *trunk;
+	struct sla_trunk_ref *trunk_ref;
+	struct sla_station_ref *station_ref;
+	char *trunk_name, *options, *cur;
+
+	options = ast_strdupa(var->value);
+	trunk_name = strsep(&options, ",");
+	
+	AST_RWLIST_RDLOCK(&sla_trunks);
+	AST_RWLIST_TRAVERSE(&sla_trunks, trunk, entry) {
+		if (!strcasecmp(trunk->name, trunk_name))
+			break;
+	}
+
+	AST_RWLIST_UNLOCK(&sla_trunks);
+	if (!trunk) {
+		ast_log(LOG_ERROR, "Trunk '%s' not found!\n", var->value);
+		return;
+	}
+	if (!(trunk_ref = create_trunk_ref(trunk)))
+		return;
+	trunk_ref->state = SLA_TRUNK_STATE_IDLE;
+
+	while ((cur = strsep(&options, ","))) {
+		char *name, *value = cur;
+		name = strsep(&value, "=");
+		if (!strcasecmp(name, "ringtimeout")) {
+			if (sscanf(value, "%u", &trunk_ref->ring_timeout) != 1) {
+				ast_log(LOG_WARNING, "Invalid ringtimeout value '%s' for "
+					"trunk '%s' on station '%s'\n", value, trunk->name, station->name);
+				trunk_ref->ring_timeout = 0;
+			}
+		} else {
+			ast_log(LOG_WARNING, "Invalid option '%s' for "
+				"trunk '%s' on station '%s'\n", name, trunk->name, station->name);
+		}
+	}
+
+	if (!(station_ref = sla_create_station_ref(station))) {
+		free(trunk_ref);
+		return;
+	}
+	ast_atomic_fetchadd_int((int *) &trunk->num_stations, 1);
+	AST_RWLIST_WRLOCK(&sla_trunks);
+	AST_LIST_INSERT_TAIL(&trunk->stations, station_ref, entry);
+	AST_RWLIST_UNLOCK(&sla_trunks);
+	AST_LIST_INSERT_TAIL(&station->trunks, trunk_ref, entry);
+}
+
+static int sla_build_station(struct ast_config *cfg, const char *cat)
 {
 	struct sla_station *station;
 	struct ast_variable *var;
@@ -3761,35 +4159,16 @@ static int build_station(struct ast_config *cfg, const char *cat)
 	ast_string_field_set(station, device, dev);
 
 	for (var = ast_variable_browse(cfg, cat); var; var = var->next) {
-		if (!strcasecmp(var->name, "trunk")) {
-			struct sla_trunk *trunk;
-			struct sla_trunk_ref *trunk_ref;
-			struct sla_station_ref *station_ref;
-			AST_RWLIST_RDLOCK(&sla_trunks);
-			AST_RWLIST_TRAVERSE(&sla_trunks, trunk, entry) {
-				if (!strcasecmp(trunk->name, var->value))
-					break;
-			}
-			AST_RWLIST_UNLOCK(&sla_trunks);
-			if (!trunk) {
-				ast_log(LOG_ERROR, "Trunk '%s' not found!\n", var->value);
-				continue;
-			}
-			if (!(trunk_ref = create_trunk_ref(trunk)))
-				continue;
-			trunk_ref->state = SLA_TRUNK_STATE_IDLE;
-			if (!(station_ref = ast_calloc(1, sizeof(*station_ref)))) {
-				free(trunk_ref);
-				continue;
-			}
-			station_ref->station = station;
-			ast_atomic_fetchadd_int((int *) &trunk->num_stations, 1);
-			AST_RWLIST_WRLOCK(&sla_trunks);
-			AST_LIST_INSERT_TAIL(&trunk->stations, station_ref, entry);
-			AST_RWLIST_UNLOCK(&sla_trunks);
-			AST_LIST_INSERT_TAIL(&station->trunks, trunk_ref, entry);
-		} else if (!strcasecmp(var->name, "autocontext")) {
+		if (!strcasecmp(var->name, "trunk"))
+			sla_add_trunk_to_station(station, var);
+		else if (!strcasecmp(var->name, "autocontext"))
 			ast_string_field_set(station, autocontext, var->value);
+		else if (!strcasecmp(var->name, "ringtimeout")) {
+			if (sscanf(var->value, "%u", &station->ring_timeout) != 1) {
+				ast_log(LOG_WARNING, "Invalid ringtimeout '%s' specified for station '%s'\n",
+					var->value, station->name);
+				station->ring_timeout = 0;
+			}
 		} else if (strcasecmp(var->name, "type") && strcasecmp(var->name, "device")) {
 			ast_log(LOG_ERROR, "Invalid option '%s' specified at line %d of %s!\n",
 				var->name, var->lineno, SLA_CONFIG_FILE);
@@ -3844,13 +4223,13 @@ static int build_station(struct ast_config *cfg, const char *cat)
 	}
 
 	AST_RWLIST_WRLOCK(&sla_stations);
-	AST_RWLIST_INSERT_HEAD(&sla_stations, station, entry);
+	AST_RWLIST_INSERT_TAIL(&sla_stations, station, entry);
 	AST_RWLIST_UNLOCK(&sla_stations);
 
 	return 0;
 }
 
-static int load_config_sla(void)
+static int sla_load_config(void)
 {
 	struct ast_config *cfg;
 	const char *cat = NULL;
@@ -3870,9 +4249,9 @@ static int load_config_sla(void)
 			continue;
 		}
 		if (!strcasecmp(type, "trunk"))
-			res = build_trunk(cfg, cat);
+			res = sla_build_trunk(cfg, cat);
 		else if (!strcasecmp(type, "station"))
-			res = build_station(cfg, cat);
+			res = sla_build_station(cfg, cat);
 		else {
 			ast_log(LOG_WARNING, "Entry in %s defined with invalid type '%s'!\n",
 				SLA_CONFIG_FILE, type);
@@ -3892,7 +4271,7 @@ static int load_config(int reload)
 
 	load_config_meetme();
 	if (!reload)
-		res = load_config_sla();
+		res = sla_load_config();
 
 	return res;
 }
@@ -3915,7 +4294,7 @@ static int unload_module(void)
 
 	ast_module_user_hangup_all();
 	
-	destroy_sla();
+	sla_destroy();
 
 	return res;
 }
diff --git a/configs/sla.conf.sample b/configs/sla.conf.sample
index a8ff93a90..839d6d936 100644
--- a/configs/sla.conf.sample
+++ b/configs/sla.conf.sample
@@ -22,6 +22,9 @@
                           ; a unique context name.  Then, in zapata.conf, this device 
                           ; should be configured to have incoming calls go to this context.
 
+;ringtimeout=30           ; Set how long to allow this trunk to ring on an inbound call before hanging 
+                          ; it up as an unanswered call.  The value is in seconds.
+
 ;[line2]
 ;type=trunk
 ;device=Zap/4
@@ -41,10 +44,6 @@
 
 ; ---- Station Declarations ------------
 
-;[station](!)                       ; In this example, all stations have the same trunks, so this 
-                                    ; configuration template is used to simplify the declaration 
-                                    ; of each station.
-
 ;type=station                       ; This line indicates that this entry is a station.
 
 ;autocontext=sla_stations           ; This supports automatic generation of the dialplan entries if 
@@ -52,13 +51,21 @@
                                     ; context without conflict.  The device for this station should 
                                     ; have its context configured to the same one listed here.
 
+;ringtimeout=10                     ; Set a timeout for how long to allow the station to ring for an 
+;                                   ; incoming call, in seconds.
+
+
 ;trunk=line1                        ; Individually list all of the trunks that will appear on this station.  This
                                     ; order is significant.  It should be the same order as they appear on the
                                     ; phone.  The order here defines the order of preference that the trunks will
                                     ; be used.
 ;trunk=line2
 ;trunk=line3
-;trunk=line4
+;trunk=line4,ringtimeout=5          ; A ring timeout for the station can also be specified for a specific trunk.
+                                    ; If a ring timeout is specified both for the whole station and for a specific
+                                    ; trunk on a station, the setting for the specific trunk will take priority.
+                                    ; This value is in seconds.
+
 
 ;[station1](station)                ; Define a station that uses the configuration from the template "station".
 ;device=SIP/station1                ; Each station must be mapped to a device.
diff --git a/doc/sla.txt b/doc/sla.txt
index 8a3eb71da..7b78001a9 100644
--- a/doc/sla.txt
+++ b/doc/sla.txt
@@ -1,17 +1,17 @@
--------------------------------------------------------------
---- Shared Line Appearances ---------------------------------
--------------------------------------------------------------
+-------------------------------------------------------------------------------
+--- Shared Line Appearances ---------------------------------------------------
+-------------------------------------------------------------------------------
 
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 INTRODUCTION
 
 The "SLA" functionality in Asterisk is intended to allow a setup that emulates
 a simple key system.  It uses the various abstraction layers already built into
 Asterisk to emulate key system functionality across various devices, including
 IP channels.
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 DIALPLAN CONFIGURATION
 
 The SLA implementation can automatically generate the dialplan necessary for
@@ -44,9 +44,9 @@ exten => station3_line1,hint,SLA:station3_line1
 exten => station3_line1,1,SLAStation(station3_line1)
 exten => station3_line2,hint,SLA:station3_line2
 exten => station3_line2,1,SLAStation(station3_line2)
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 TRUNKS
 
 For the trunk side of SLA, the only channels that are currently supported are
@@ -57,10 +57,10 @@ Be sure to configure the trunk's context to be the same one that is set for the
 
 If the dialplan is being built manually, ensure that calls coming in on a trunk
 execute the SLATrunk() application with an argument of the trunk name.
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 
 
--------------------------------------------------------------
+-------------------------------------------------------------------------------
 STATIONS
 
 Currently, the only channel driver that has all of the features necessary to
@@ -90,4 +90,4 @@ a SIP phone for use with SLA:
    c) If you would like the phone to automatically connect to a trunk when it
       is taken off hook, then the phone should be automatically configured to
       dial "station1" when it is taken off hook.
--------------------------------------------------------------
+-------------------------------------------------------------------------------
diff --git a/main/dial.c b/main/dial.c
index af3c5e354..9536629e9 100644
--- a/main/dial.c
+++ b/main/dial.c
@@ -559,7 +559,7 @@ enum ast_dial_result ast_dial_run(struct ast_dial *dial, struct ast_channel *cha
 
 	/* If we are running async spawn a thread and send it away... otherwise block here */
 	if (async) {
-		set_state(dial, AST_DIAL_RESULT_TRYING);
+		dial->state = AST_DIAL_RESULT_TRYING;
 		/* Try to create a thread */
 		if (ast_pthread_create(&dial->thread, NULL, async_dial, dial)) {
 			/* Failed to create the thread - hangup all dialed channels and return failed */