bridge_multiplexed: Keep the multiplexed thread until no more bridges use it.

* Fixed the potential of losing the multiplexed bridge thread when the
last channel leaves and another joins while the multiplexed thread is
being shut down.

* Refactored and improved the management of the serviced channels array.

* Changed the channels count to a bridges count so it only needs to be
incremented rather than changed by two.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@380666 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 136 insertions, 72 deletions

diff --git a/bridges/bridge_multiplexed.c b/bridges/bridge_multiplexed.c
index cb59b8a65..309ad47e3 100644
--- a/bridges/bridge_multiplexed.c
+++ b/bridges/bridge_multiplexed.c
@@ -50,23 +50,23 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
 /*! \brief Number of buckets our multiplexed thread container can have */
 #define MULTIPLEXED_BUCKETS 53
 
-/*! \brief Number of channels we handle in a single thread */
-#define MULTIPLEXED_MAX_CHANNELS 8
+/*! \brief Number of bridges we handle in a single thread */
+#define MULTIPLEXED_MAX_BRIDGES		4
 
 /*! \brief Structure which represents a single thread handling multiple 2 channel bridges */
 struct multiplexed_thread {
 	/*! Thread itself */
 	pthread_t thread;
+	/*! Channels serviced by this thread */
+	struct ast_channel *chans[2 * MULTIPLEXED_MAX_BRIDGES];
 	/*! Pipe used to wake up the multiplexed thread */
 	int pipe[2];
-	/*! Channels in this thread */
-	struct ast_channel *chans[MULTIPLEXED_MAX_CHANNELS];
-	/*! Number of channels in this thread */
-	unsigned int count;
-	/*! Bit used to indicate that the thread is waiting on channels */
-	unsigned int waiting:1;
 	/*! Number of channels actually being serviced by this thread */
 	unsigned int service_count;
+	/*! Number of bridges in this thread */
+	unsigned int bridges;
+	/*! TRUE if the thread is waiting on channels */
+	unsigned int waiting:1;
 };
 
 /*! \brief Container of all operating multiplexed threads */
@@ -76,7 +76,8 @@ static struct ao2_container *muxed_threads;
 static int find_multiplexed_thread(void *obj, void *arg, int flags)
 {
 	struct multiplexed_thread *muxed_thread = obj;
-	return (muxed_thread->count <= (MULTIPLEXED_MAX_CHANNELS - 2)) ? CMP_MATCH | CMP_STOP : 0;
+
+	return (muxed_thread->bridges < MULTIPLEXED_MAX_BRIDGES) ? CMP_MATCH | CMP_STOP : 0;
 }
 
 /*! \brief Destroy callback for a multiplexed thread structure */
@@ -147,8 +148,8 @@ static int multiplexed_bridge_create(struct ast_bridge *bridge)
 		ast_debug(1, "Found multiplexed thread '%p' for bridge '%p'\n", muxed_thread, bridge);
 	}
 
-	/* Bump the count of the thread structure up by two since the channels for this bridge will be joining shortly */
-	muxed_thread->count += 2;
+	/* Increase the number of bridges using this multiplexed bridge */
+	++muxed_thread->bridges;
 
 	ao2_unlock(muxed_threads);
 
@@ -157,7 +158,17 @@ static int multiplexed_bridge_create(struct ast_bridge *bridge)
 	return 0;
 }
 
-/*! \brief Internal function which nudges the thread */
+/*!
+ * \internal
+ * \brief Nudges the multiplex thread.
+ * \since 12.0.0
+ *
+ * \param muxed_thread Controller to poke the thread.
+ *
+ * \note This function assumes the muxed_thread is locked.
+ *
+ * \return Nothing
+ */
 static void multiplexed_nudge(struct multiplexed_thread *muxed_thread)
 {
 	int nudge = 0;
@@ -179,28 +190,39 @@ static void multiplexed_nudge(struct multiplexed_thread *muxed_thread)
 static int multiplexed_bridge_destroy(struct ast_bridge *bridge)
 {
 	struct multiplexed_thread *muxed_thread;
+	pthread_t thread;
 
 	muxed_thread = bridge->bridge_pvt;
 	if (!muxed_thread) {
 		return -1;
 	}
+	bridge->bridge_pvt = NULL;
 
 	ao2_lock(muxed_threads);
 
-	muxed_thread->count -= 2;
-
-	if (!muxed_thread->count) {
-		ast_debug(1, "Unlinking multiplexed thread '%p' since nobody is using it anymore\n", muxed_thread);
+	if (--muxed_thread->bridges) {
+		/* Other bridges are still using the multiplexed thread. */
+		ao2_unlock(muxed_threads);
+	} else {
+		ast_debug(1, "Unlinking multiplexed thread '%p' since nobody is using it anymore\n",
+			muxed_thread);
 		ao2_unlink(muxed_threads, muxed_thread);
-	}
+		ao2_unlock(muxed_threads);
 
-	multiplexed_nudge(muxed_thread);
+		/* Stop the multiplexed bridge thread. */
+		ao2_lock(muxed_thread);
+		multiplexed_nudge(muxed_thread);
+		thread = muxed_thread->thread;
+		muxed_thread->thread = AST_PTHREADT_STOP;
+		ao2_unlock(muxed_thread);
 
-	ao2_unlock(muxed_threads);
+		if (thread != AST_PTHREADT_NULL) {
+			/* Wait for multiplexed bridge thread to die. */
+			pthread_join(thread, NULL);
+		}
+	}
 
 	ao2_ref(muxed_thread, -1);
-	bridge->bridge_pvt = NULL;
-
 	return 0;
 }
 
@@ -210,20 +232,24 @@ static void *multiplexed_thread_function(void *data)
 	struct multiplexed_thread *muxed_thread = data;
 	int fds = muxed_thread->pipe[0];
 
-	ao2_lock(muxed_thread);
-
 	ast_debug(1, "Starting actual thread for multiplexed thread '%p'\n", muxed_thread);
 
+	ao2_lock(muxed_thread);
+
 	while (muxed_thread->thread != AST_PTHREADT_STOP) {
 		struct ast_channel *winner;
-		struct ast_channel *first = muxed_thread->chans[0];
 		int to = -1;
 		int outfd = -1;
 
-		/* Move channels around so not just the first one gets priority */
-		memmove(muxed_thread->chans, muxed_thread->chans + 1,
-			sizeof(struct ast_channel *) * (muxed_thread->service_count - 1));
-		muxed_thread->chans[muxed_thread->service_count - 1] = first;
+		if (1 < muxed_thread->service_count) {
+			struct ast_channel *first;
+
+			/* Move channels around so not just the first one gets priority */
+			first = muxed_thread->chans[0];
+			memmove(muxed_thread->chans, muxed_thread->chans + 1,
+				sizeof(struct ast_channel *) * (muxed_thread->service_count - 1));
+			muxed_thread->chans[muxed_thread->service_count - 1] = first;
+		}
 
 		muxed_thread->waiting = 1;
 		ao2_unlock(muxed_thread);
@@ -263,70 +289,108 @@ static void *multiplexed_thread_function(void *data)
 		}
 	}
 
-	muxed_thread->thread = AST_PTHREADT_NULL;
+	ao2_unlock(muxed_thread);
 
 	ast_debug(1, "Stopping actual thread for multiplexed thread '%p'\n", muxed_thread);
-
-	ao2_unlock(muxed_thread);
 	ao2_ref(muxed_thread, -1);
 
 	return NULL;
 }
 
-/*! \brief Helper function which adds or removes a channel and nudges the thread */
-static void multiplexed_add_or_remove(struct multiplexed_thread *muxed_thread, struct ast_channel *chan, int add)
+/*!
+ * \internal
+ * \brief Check to see if the multiplexed bridge thread needs to be started.
+ * \since 12.0.0
+ *
+ * \param muxed_thread Controller to check if need to start thread.
+ *
+ * \note This function assumes the muxed_thread is locked.
+ *
+ * \return Nothing
+ */
+static void multiplexed_thread_start(struct multiplexed_thread *muxed_thread)
+{
+	if (muxed_thread->service_count && muxed_thread->thread == AST_PTHREADT_NULL) {
+		ao2_ref(muxed_thread, +1);
+		if (ast_pthread_create(&muxed_thread->thread, NULL, multiplexed_thread_function, muxed_thread)) {
+			muxed_thread->thread = AST_PTHREADT_NULL;/* For paranoia's sake. */
+			ao2_ref(muxed_thread, -1);
+			ast_log(LOG_WARNING, "Failed to create the common thread for multiplexed thread '%p', trying next time\n",
+				muxed_thread);
+		}
+	}
+}
+
+/*!
+ * \internal
+ * \brief Add a channel to the multiplexed bridge.
+ * \since 12.0.0
+ *
+ * \param muxed_thread Controller to add a channel.
+ * \param chan Channel to add to the channel service array.
+ *
+ * \return Nothing
+ */
+static void multiplexed_chan_add(struct multiplexed_thread *muxed_thread, struct ast_channel *chan)
 {
 	int idx;
-	pthread_t thread = AST_PTHREADT_NULL;
 
 	ao2_lock(muxed_thread);
 
 	multiplexed_nudge(muxed_thread);
 
-	for (idx = 0; idx < ARRAY_LEN(muxed_thread->chans); ++idx) {
+	/* Check if already in the channel service array for safety. */
+	for (idx = 0; idx < muxed_thread->service_count; ++idx) {
 		if (muxed_thread->chans[idx] == chan) {
-			if (!add) {
-				memmove(muxed_thread->chans + idx,
-					muxed_thread->chans + idx + 1,
-					sizeof(struct ast_channel *) * (ARRAY_LEN(muxed_thread->chans) - (idx + 1)));
-				muxed_thread->chans[ARRAY_LEN(muxed_thread->chans) - 1] = NULL;
-				--muxed_thread->service_count;
-			}
-			break;
-		}
-		if (!muxed_thread->chans[idx]) {
-			if (add) {
-				muxed_thread->chans[idx] = chan;
-				++muxed_thread->service_count;
-			}
 			break;
 		}
 	}
-	if (ARRAY_LEN(muxed_thread->chans) == idx && add) {
-		ast_log(LOG_ERROR, "Could not add channel %s to multiplexed thread %p.  Array not large enough.\n",
-			ast_channel_name(chan), muxed_thread);
-		ast_assert(0);
-	}
-
-	if (muxed_thread->service_count && muxed_thread->thread == AST_PTHREADT_NULL) {
-		ao2_ref(muxed_thread, +1);
-		if (ast_pthread_create(&muxed_thread->thread, NULL, multiplexed_thread_function, muxed_thread)) {
-			ao2_ref(muxed_thread, -1);
-			ast_log(LOG_WARNING, "Failed to create the bridge thread for multiplexed thread '%p', trying next time\n",
-				muxed_thread);
+	if (idx == muxed_thread->service_count) {
+		/* Channel to add was not already in the array. */
+		if (muxed_thread->service_count < ARRAY_LEN(muxed_thread->chans)) {
+			muxed_thread->chans[muxed_thread->service_count++] = chan;
+		} else {
+			ast_log(LOG_ERROR, "Could not add channel %s to multiplexed thread %p.  Array not large enough.\n",
+				ast_channel_name(chan), muxed_thread);
+			ast_assert(0);
 		}
-	} else if (!muxed_thread->service_count
-		&& muxed_thread->thread != AST_PTHREADT_NULL
-		&& muxed_thread->thread != AST_PTHREADT_STOP) {
-		thread = muxed_thread->thread;
-		muxed_thread->thread = AST_PTHREADT_STOP;
 	}
 
+	multiplexed_thread_start(muxed_thread);
+
 	ao2_unlock(muxed_thread);
+}
 
-	if (thread != AST_PTHREADT_NULL) {
-		pthread_join(thread, NULL);
+/*!
+ * \internal
+ * \brief Remove a channel from the multiplexed bridge.
+ * \since 12.0.0
+ *
+ * \param muxed_thread Controller to remove a channel.
+ * \param chan Channel to remove from the channel service array.
+ *
+ * \return Nothing
+ */
+static void multiplexed_chan_remove(struct multiplexed_thread *muxed_thread, struct ast_channel *chan)
+{
+	int idx;
+
+	ao2_lock(muxed_thread);
+
+	multiplexed_nudge(muxed_thread);
+
+	/* Remove channel from service array. */
+	for (idx = 0; idx < muxed_thread->service_count; ++idx) {
+		if (muxed_thread->chans[idx] != chan) {
+			continue;
+		}
+		muxed_thread->chans[idx] = muxed_thread->chans[--muxed_thread->service_count];
+		break;
 	}
+
+	multiplexed_thread_start(muxed_thread);
+
+	ao2_unlock(muxed_thread);
 }
 
 /*! \brief Join function which actually adds the channel into the array to be monitored */
@@ -338,7 +402,7 @@ static int multiplexed_bridge_join(struct ast_bridge *bridge, struct ast_bridge_
 
 	ast_debug(1, "Adding channel '%s' to multiplexed thread '%p' for monitoring\n", ast_channel_name(bridge_channel->chan), muxed_thread);
 
-	multiplexed_add_or_remove(muxed_thread, bridge_channel->chan, 1);
+	multiplexed_chan_add(muxed_thread, bridge_channel->chan);
 
 	/* If the second channel has not yet joined do not make things compatible */
 	if (c0 == c1) {
@@ -361,7 +425,7 @@ static int multiplexed_bridge_leave(struct ast_bridge *bridge, struct ast_bridge
 
 	ast_debug(1, "Removing channel '%s' from multiplexed thread '%p'\n", ast_channel_name(bridge_channel->chan), muxed_thread);
 
-	multiplexed_add_or_remove(muxed_thread, bridge_channel->chan, 0);
+	multiplexed_chan_remove(muxed_thread, bridge_channel->chan);
 
 	return 0;
 }
@@ -373,7 +437,7 @@ static void multiplexed_bridge_suspend(struct ast_bridge *bridge, struct ast_bri
 
 	ast_debug(1, "Suspending channel '%s' from multiplexed thread '%p'\n", ast_channel_name(bridge_channel->chan), muxed_thread);
 
-	multiplexed_add_or_remove(muxed_thread, bridge_channel->chan, 0);
+	multiplexed_chan_remove(muxed_thread, bridge_channel->chan);
 }
 
 /*! \brief Unsuspend function which means control of the channel is coming back to us */
@@ -383,7 +447,7 @@ static void multiplexed_bridge_unsuspend(struct ast_bridge *bridge, struct ast_b
 
 	ast_debug(1, "Unsuspending channel '%s' from multiplexed thread '%p'\n", ast_channel_name(bridge_channel->chan), muxed_thread);
 
-	multiplexed_add_or_remove(muxed_thread, bridge_channel->chan, 1);
+	multiplexed_chan_add(muxed_thread, bridge_channel->chan);
 }
 
 /*! \brief Write function for writing frames into the bridge */