diff --git a/main/threadpool.c b/main/threadpool.c
index 362c765cff..15450bc2ff 100644
--- a/main/threadpool.c
+++ b/main/threadpool.c
@@ -22,7 +22,16 @@
 #include "asterisk/threadpool.h"
 #include "asterisk/taskprocessor.h"
 
-struct ast_threadpool;
+#define THREAD_BUCKETS 89
+
+static int id_counter;
+
+struct ast_threadpool {
+	struct ast_threadpool_listener *threadpool_listener;
+	struct ao2_container *active_threads;
+	struct ao2_container *idle_threads;
+	struct ao2_container *zombie_threads;
+}
 
 enum worker_state {
 	ALIVE,
@@ -31,15 +40,131 @@ enum worker_state {
 };
 
 struct worker_thread {
+	int id;
 	ast_cond_t cond;
 	ast_mutex_t lock;
 	pthread_t thread;
 	struct ast_threadpool *pool;
-	AST_LIST_ENTRY(struct worker_thread) next;
-	int wake_up;
 	enum worker_state state;
+	int wake_up;
 };
 
+static int worker_thread_hash(const void *obj)
+{
+	struct worker_thread *worker= obj;
+
+	return worker->id;
+}
+
+static int worker_thread_cmp(void *obj, void *arg, int flags)
+{
+	struct worker_thread *worker1 = obj;
+	struct worker_thread *worker2 = arg;
+
+	return worker1->id == worker2->id ? CMP_MATCH : 0;
+}
+
+static worker_thread *worker_thread_alloc(struct ast_threadpool *pool)
+{
+	struct worker_thread *worker = ao2_alloc(1, sizeof(*worker));
+	if (!worker) {
+		/* XXX Dangit! */
+		return NULL;
+	}
+	worker->id = ast_atomic_fetchadd_int(&id_counter, 1);
+	ast_mutex_init(&worker->lock);
+	ast_cond_init(&worker->cond, NULL);
+	worker->pool = pool;
+	worker->thread = AST_PTHREADT_NULL;
+	worker->state = ALIVE;
+	if (ast_pthread_create(&worker->thread, NULL, worker_active, worker) < 0) {
+		/* XXX Poop! */
+		ao2_ref(worker, -1);
+		return NULL;
+	}
+	return worker;
+}
+
+static void threadpool_send_state_changed(struct ast_threadpool *pool)
+{
+	int active_size = ao2_container_count(pool->active_threads);
+	int idle_size = ao2_container_count(pool->idle_threads);
+	int zombie_size = ao2_container_count(pool->zombie_threads);
+
+	pool->listener->callbacks->state_changed(pool->listener, active_size, idle_size, zombie_size);
+}
+
+struct thread_worker_pair {
+	struct ast_threadpool *pool;
+	struct worker_thread *worker;
+};
+
+static void thread_worker_pair_destructor(void *obj)
+{
+	struct thread_worker_pair *pair = obj;
+	ao2_ref(pair->pool, -1);
+	ao2_ref(pair->worker, -1);
+}
+
+struct thread_worker_pair *thread_worker_pair_init(struct ast_threadpool *pool,
+		struct worker_thread *worker)
+{
+	struct thread_worker_pair *pair = ao2_alloc(sizeof(*pair), thread_worker_pair_destructor);
+	if (!pair) {
+		/*XXX Crap */
+		return NULL;
+	}
+	pair->pool = ao2_ref(pool);
+	pair->worker = ao2_ref(worker);
+	return pair;
+}
+
+static int queued_active_thread_idle(void *data)
+{
+	struct thread_worker_pair *pair = data;
+
+	ao2_link(pair->pool->idle_threads, pair->worker);
+	ao2_unlink(pair->pool->active_threads, pair->worker);
+
+	threadpool_send_state_changed(pair->pool);
+
+	ao2_ref(pair, -1);
+	return 0;
+}
+
+static void threadpool_active_thread_idle(struct ast_threadpool *pool,
+		struct worker_thread *worker)
+{
+	struct thread_worker_pair *pair = thread_worker_pair_init(pool, worker);
+	if (!pair) {
+		/*XXX Crap */
+		return;
+	}
+	ast_taskprocessor_push(pool->control_tps, queued_active_thread_idle(pair));
+}
+
+static int queued_zombie_thread_dead(void *data)
+{
+	struct thread_worker_pair *pair = data;
+
+	ao2_unlink(pair->pool->zombie_threads, pair->worker);
+	threadpool_send_state_changed(pair->pool);
+
+	ao2_ref(pair, -1);
+	return 0;
+}
+
+static void threadpool_zombie_thread_dead(struct ast_threadpool *pool,
+		struct worker_thread *worker)
+{
+	struct thread_worker_pair *pair = thread_worker_pair_init(pool, worker);
+	if (!pair) {
+		/* XXX Crap */
+		return;
+	}
+	ast_taskprocessor_push(pool->control_tps, queued_zombie_thread_dead(pair));
+}
+
 static int worker_idle(struct worker_thread *worker)
 {
 	SCOPED_MUTEX(lock, &worker->lock);
@@ -78,19 +203,31 @@ static int worker_active(struct worker_thread *worker)
 	return 0;
 }
 
-struct ast_threadpool {
-	struct ast_threadpool_listener *threadpool_listener;
-	int active_threads;
-	int idle_threads;
-	int zombie_threads;
-}
 
 static void *threadpool_tps_listener_alloc(struct ast_taskprocessor_listener *listener)
 {
-	RAII_VAR(ast_threadpool *, threadpool,
-			ao2_alloc(sizeof(*threadpool), threadpool_destroy), ao2_cleanup);
+	RAII_VAR(ast_threadpool *, pool,
+			ao2_alloc(sizeof(*pool), threadpool_destroy), ao2_cleanup);
 
-	return threadpool;
+	pool->control_tps = ast_taskprocessor_get(/* XXX ??? */, TPS_REF_DEFAULT);
+	if (!pool->control_tps) {
+		return NULL;
+	}
+	pool->active_threads = ao2_container_alloc(THREAD_BUCKETS, worker_thread_hash, worker_thread_cmp);
+	if (!pool->active_threads) {
+		return NULL;
+	}
+	pool->idle_threads = ao2_container_alloc(THREAD_BUCKETS, worker_thread_hash, worker_thread_cmp);
+	if (!pool->idle_threads) {
+		return NULL;
+	}
+	pool->zombie_threads = ao2_container_alloc(THREAD_BUCKETS, worker_thread_hash, worker_thread_cmp);
+	if (!pool->zombie_thread) {
+		return NULL;
+	}
+
+	ao2_ref(pool, +1);
+	return pool;
 }
 
 static void threadpool_tps_task_pushed(struct ast_taskprocessor_listener *listener)
@@ -140,8 +277,116 @@ static struct ast_taskprocessor_listener *threadpool_tps_alloc(void)
 	return ast_taskprocessor_create_with_listener(tps_listener);
 }
 
+static void grow(struct ast_threadpool *pool, int delta)
+{
+	int i;
+	for (i = 0; i < delta; ++i) {
+		struct worker_thread *worker = worker_thread_alloc(pool);
+		if (!worker) {
+			/* XXX Abandon */
+			return;
+		}
+		ao2_link(pool->active_threads, worker);
+	}
+}
+
+static int kill_threads(void *obj, void *arg, int flags)
+{
+	int *num_to_kill = arg;
+
+	if ((*num_to_kill)-- > 0) {
+		return CMP_MATCH;
+	} else {
+		return CMP_STOP;
+	}
+}
+
+static int zombify_threads(void *obj, void *arg, void *data, int flags)
+{
+	struct worker_thread *worker = obj;
+	struct ast_threadpool *pool = arg;
+	int *num_to_zombify = data;
+
+	if ((*num_to_zombify)-- > 0) {
+		ao2_link(pool->zombie_threads, worker);
+		return CMP_MATCH;
+	} else {
+		return CMP_STOP;
+	}
+}
+
+static void shrink(struct ast_threadpool *pool, int delta)
+{
+	/* 
+	 * Preference is to kill idle threads, but
+	 * we'll move on to deactivating active threads
+	 * if we have to
+	 */
+	int idle_threads = ao2_container_count(pool->idle_threads);
+	int idle_threads_to_kill = MIN(delta, idle_threads);
+	int active_threads_to_zombify = delta - idle_threads_to_kill;
+	int i = 0;
+
+	ao2_callback(pool->idle_threads, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE | OBJ_NOLOCK,
+			kill_threads, &idle_threads_to_kill);
+
+	ao2_callback_data(pool->active_threads, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE | OBJ_NOLOCK,
+			zombify_threads, pool, &active_threads_to_zombify);
+}
+
+struct set_size_data {
+	struct threadpool *pool;
+	int size;
+};
+
+void set_size_data_destroy(void *obj)
+{
+	struct set_size_data *ssd = obj;
+	ao2_ref(ssd->pool, -1);
+}
+
+static int queued_set_size(void *data)
+{
+	struct set_size_data *ssd = data;
+	struct ast_threadpool *pool = ssd->pool;
+	int num_threads = ssd->size;
+
+	/* We don't count zombie threads as being "live when potentially resizing */
+	int current_size = ao2_container_count(pool->active_threads) +
+		ao2_container_count(pool->idle_threads);
+
+	if (current_size = num_threads) {
+		return 0;
+	}
+
+	if (current_size < num_threads) {
+		grow(pool, num_threads - current_size);
+	} else {
+		shrink(pool, current_size - num_threads);
+	}
+
+	threadpool_send_state_changed(pool);
+	ao2_ref(set_size_data, -1);
+}
+
 void ast_threadpool_set_size(struct ast_threadpool *pool, int size)
 {
+	struct set_size_data *ssd;
+	if (size < 0) {
+		ast_log(LOG_WARNING, "Invalid threadpool size used for resizing: %d\n", size);
+		return;
+	}
+
+	ssd = ao2_alloc(sizeof(*ssd), set_size_data_destroy);
+	if (!ssd) {
+		/* XXX Crap */
+		return;
+	}
+
+	ssd->pool = ao2_ref(pool);
+	ssd->size = size;
+
+	ast_taskprocessor_push(pool->control_tps, queued_set_size, ssd);
 }
 
 struct ast_threadpool *ast_threadpool_create(struct ast_threadpool_listener *listener, int initial_size)