Named call pickup groups. Fixes, missing functionality, and improvements.

* ASTERISK-20383
Missing named call pickup group features:

CHANNEL(callgroup) - Need CHANNEL(namedcallgroup)
CHANNEL(pickupgroup) - Need CHANNEL(namedpickupgroup)
Pickup() - Needs to also select from named pickup groups.

* ASTERISK-20384
Using the pickupexten, the pickup channel selection could fail even though
there was a call it could have picked up.  In a call pickup race when
there are multiple calls to pickup and two extensions try to pickup a
call, it is conceivable that the loser will not pick up any call even
though it could have picked up the next oldest matching call.

Regression because of the named call pickup group feature.

* See ASTERISK-20386 for the implementation improvements.  These are the
changes in channel.c and channel.h.

* Fixed some locking issues in CHANNEL().

(closes issue ASTERISK-20383)
Reported by: rmudgett
(closes issue ASTERISK-20384)
Reported by: rmudgett
(closes issue ASTERISK-20386)
Reported by: rmudgett
Tested by: rmudgett

Review: https://reviewboard.asterisk.org/r/2112/
........

Merged revisions 373220 from http://svn.asterisk.org/svn/asterisk/branches/11


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@373221 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 86 insertions, 50 deletions

diff --git a/main/features.c b/main/features.c
index 0650129c0..f89ca816d 100644
--- a/main/features.c
+++ b/main/features.c
@@ -7707,80 +7707,117 @@ int ast_can_pickup(struct ast_channel *chan)
 static int find_channel_by_group(void *obj, void *arg, void *data, int flags)
 {
 	struct ast_channel *target = obj;/*!< Potential pickup target */
-	struct ast_channel *chan = data;/*!< Channel wanting to pickup call */
+	struct ast_channel *chan = arg;/*!< Channel wanting to pickup call */
+
+	if (chan == target) {
+		return 0;
+	}
 
 	ast_channel_lock(target);
+	if (ast_can_pickup(target)) {
+		/* Lock both channels. */
+		while (ast_channel_trylock(chan)) {
+			ast_channel_unlock(target);
+			sched_yield();
+			ast_channel_lock(target);
+		}
 
-	/*
-	 * Both, callgroup and namedcallgroup pickup variants are matched independently.
-	 * Checking for named group match is done last since it's a rather expensive operation.
-	 */
-	if (chan != target && ast_can_pickup(target)
-		&& ((ast_channel_pickupgroup(chan) & ast_channel_callgroup(target))
-			|| (ast_namedgroups_intersect(ast_channel_named_pickupgroups(chan), ast_channel_named_callgroups(target))))) {
 		/*
-		 * Return with the channel unlocked on purpose, else we would lock many channels with the chance for deadlock
+		 * Both callgroup and namedcallgroup pickup variants are
+		 * matched independently.  Checking for named group match is
+		 * done last since it's a more expensive operation.
 		 */
-		ast_channel_unlock(target);
-		return CMP_MATCH;
+		if ((ast_channel_pickupgroup(chan) & ast_channel_callgroup(target))
+			|| (ast_namedgroups_intersect(ast_channel_named_pickupgroups(chan),
+				ast_channel_named_callgroups(target)))) {
+			struct ao2_container *candidates = data;/*!< Candidate channels found. */
+
+			/* This is a candidate to pickup */
+			ao2_link(candidates, target);
+		}
+		ast_channel_unlock(chan);
 	}
 	ast_channel_unlock(target);
 
 	return 0;
 }
 
-/*!
- * \brief Pickup a call
- * \param chan channel that initiated pickup.
- *
- * Walk list of channels, checking it is not itself, channel is pbx one,
- * check that the callgroup for both channels are the same and the channel is ringing.
- * Answer calling channel, flag channel as answered on queue, masq channels together.
- */
-int ast_pickup_call(struct ast_channel *chan)
+struct ast_channel *ast_pickup_find_by_group(struct ast_channel *chan)
 {
+	struct ao2_container *candidates;/*!< Candidate channels found to pickup. */
 	struct ast_channel *target;/*!< Potential pickup target */
-	struct ao2_iterator *targets_it;/*!< Potential pickup targets, must find the oldest of them */
-	struct ast_channel *candidate;/*!< Potential new older target */
-	int res = -1;
-	ast_debug(1, "pickup attempt by %s\n", ast_channel_name(chan));
 
-	/*
-	 * Transfer all pickup-able channels to another container-iterator.
-	 * Iterate it to find the oldest channel.
-	 */
-	targets_it = (struct ao2_iterator *) ast_channel_callback(find_channel_by_group,
-		NULL, chan, OBJ_MULTIPLE);
-	if (!targets_it) {
-		/* Search really failed. */
-		goto no_pickup_calls;
+	candidates = ao2_container_alloc_options(AO2_ALLOC_OPT_LOCK_NOLOCK, 1, NULL, NULL);
+	if (!candidates) {
+		return NULL;
 	}
 
+	/* Find all candidate targets by group. */
+	ast_channel_callback(find_channel_by_group, chan, candidates, 0);
+
+	/* Find the oldest pickup target candidate */
 	target = NULL;
-	while ((candidate = ao2_iterator_next(targets_it))) {
-		if (!target) {
-			target = candidate;
-			continue;
+	for (;;) {
+		struct ast_channel *candidate;/*!< Potential new older target */
+		struct ao2_iterator iter;
+
+		iter = ao2_iterator_init(candidates, 0);
+		while ((candidate = ao2_iterator_next(&iter))) {
+			if (!target) {
+				/* First target. */
+				target = candidate;
+				continue;
+			}
+			if (ast_tvcmp(ast_channel_creationtime(candidate), ast_channel_creationtime(target)) < 0) {
+				/* We have a new target. */
+				ast_channel_unref(target);
+				target = candidate;
+				continue;
+			}
+			ast_channel_unref(candidate);
 		}
-		if (ast_tvcmp(ast_channel_creationtime(candidate), ast_channel_creationtime(target)) < 0) {
-			ast_channel_unref(target);
-			target = candidate;
-			continue;
+		ao2_iterator_destroy(&iter);
+		if (!target) {
+			/* No candidates found. */
+			break;
 		}
-		ast_channel_unref(candidate);
-	}
-	ao2_iterator_destroy(targets_it);
-	if (target) {
+
 		/* The found channel must be locked and ref'd. */
 		ast_channel_lock(target);
+
 		/* Recheck pickup ability */
-		if (!ast_can_pickup(target)) {
-			/* Someone else picked it up or the call went away. */
-			ast_channel_unlock(target);
-			target = ast_channel_unref(target);
+		if (ast_can_pickup(target)) {
+			/* This is the channel to pickup. */
+			break;
 		}
+
+		/* Someone else picked it up or the call went away. */
+		ast_channel_unlock(target);
+		ao2_unlink(candidates, target);
+		target = ast_channel_unref(target);
 	}
+	ao2_ref(candidates, -1);
+
+	return target;
+}
+
+/*!
+ * \brief Pickup a call
+ * \param chan channel that initiated pickup.
+ *
+ * Walk list of channels, checking it is not itself, channel is pbx one,
+ * check that the callgroup for both channels are the same and the channel is ringing.
+ * Answer calling channel, flag channel as answered on queue, masq channels together.
+ */
+int ast_pickup_call(struct ast_channel *chan)
+{
+	struct ast_channel *target;/*!< Potential pickup target */
+	int res = -1;
+
+	ast_debug(1, "pickup attempt by %s\n", ast_channel_name(chan));
 
+	/* The found channel is already locked. */
+	target = ast_pickup_find_by_group(chan);
 	if (target) {
 		ast_log(LOG_NOTICE, "pickup %s attempt by %s\n", ast_channel_name(target), ast_channel_name(chan));
 
@@ -7796,7 +7833,6 @@ int ast_pickup_call(struct ast_channel *chan)
 		target = ast_channel_unref(target);
 	}
 
-no_pickup_calls:
 	if (res < 0) {
 		ast_debug(1, "No call pickup possible... for %s\n", ast_channel_name(chan));
 		if (!ast_strlen_zero(pickupfailsound)) {