threadpool, res_pjsip: Add serializer group shutdown API calls.

A module trying to unload needs to wait for all serializers it creates and
uses to complete processing before unloading.

ASTERISK-24907
Reported by: Kevin Harwell

Change-Id: I8c80b90f2f82754e8dbb02ddf3c9121e5e966059

main/threadpool.c

@@ -1126,18 +1126,126 @@ static void worker_set_state(struct worker_thread *worker, enum worker_state sta
 	ast_cond_signal(&worker->cond);
 }
 
+/*! Serializer group shutdown control object. */
+struct ast_serializer_shutdown_group {
+	/*! Shutdown thread waits on this conditional. */
+	ast_cond_t cond;
+	/*! Count of serializers needing to shutdown. */
+	int count;
+};
+
+static void serializer_shutdown_group_dtor(void *vdoomed)
+{
+	struct ast_serializer_shutdown_group *doomed = vdoomed;
+
+	ast_cond_destroy(&doomed->cond);
+}
+
+struct ast_serializer_shutdown_group *ast_serializer_shutdown_group_alloc(void)
+{
+	struct ast_serializer_shutdown_group *shutdown_group;
+
+	shutdown_group = ao2_alloc(sizeof(*shutdown_group), serializer_shutdown_group_dtor);
+	if (!shutdown_group) {
+		return NULL;
+	}
+	ast_cond_init(&shutdown_group->cond, NULL);
+	return shutdown_group;
+}
+
+int ast_serializer_shutdown_group_join(struct ast_serializer_shutdown_group *shutdown_group, int timeout)
+{
+	int remaining;
+	ast_mutex_t *lock;
+
+	if (!shutdown_group) {
+		return 0;
+	}
+
+	lock = ao2_object_get_lockaddr(shutdown_group);
+	ast_assert(lock != NULL);
+
+	ao2_lock(shutdown_group);
+	if (timeout) {
+		struct timeval start;
+		struct timespec end;
+
+		start = ast_tvnow();
+		end.tv_sec = start.tv_sec + timeout;
+		end.tv_nsec = start.tv_usec * 1000;
+		while (shutdown_group->count) {
+			if (ast_cond_timedwait(&shutdown_group->cond, lock, &end)) {
+				/* Error or timed out waiting for the count to reach zero. */
+				break;
+			}
+		}
+	} else {
+		while (shutdown_group->count) {
+			if (ast_cond_wait(&shutdown_group->cond, lock)) {
+				/* Error */
+				break;
+			}
+		}
+	}
+	remaining = shutdown_group->count;
+	ao2_unlock(shutdown_group);
+	return remaining;
+}
+
+/*!
+ * \internal
+ * \brief Increment the number of serializer members in the group.
+ * \since 13.5.0
+ *
+ * \param shutdown_group Group shutdown controller.
+ *
+ * \return Nothing
+ */
+static void serializer_shutdown_group_inc(struct ast_serializer_shutdown_group *shutdown_group)
+{
+	ao2_lock(shutdown_group);
+	++shutdown_group->count;
+	ao2_unlock(shutdown_group);
+}
+
+/*!
+ * \internal
+ * \brief Decrement the number of serializer members in the group.
+ * \since 13.5.0
+ *
+ * \param shutdown_group Group shutdown controller.
+ *
+ * \return Nothing
+ */
+static void serializer_shutdown_group_dec(struct ast_serializer_shutdown_group *shutdown_group)
+{
+	ao2_lock(shutdown_group);
+	--shutdown_group->count;
+	if (!shutdown_group->count) {
+		ast_cond_signal(&shutdown_group->cond);
+	}
+	ao2_unlock(shutdown_group);
+}
+
 struct serializer {
+	/*! Threadpool the serializer will use to process the jobs. */
 	struct ast_threadpool *pool;
+	/*! Which group will wait for this serializer to shutdown. */
+	struct ast_serializer_shutdown_group *shutdown_group;
 };
 
 static void serializer_dtor(void *obj)
 {
 	struct serializer *ser = obj;
+
 	ao2_cleanup(ser->pool);
 	ser->pool = NULL;
+	ao2_cleanup(ser->shutdown_group);
+	ser->shutdown_group = NULL;
 }
 
-static struct serializer *serializer_create(struct ast_threadpool *pool)
+static struct serializer *serializer_create(struct ast_threadpool *pool,
+	struct ast_serializer_shutdown_group *shutdown_group)
 {
 	struct serializer *ser;
 
@@ -1147,6 +1255,7 @@ static struct serializer *serializer_create(struct ast_threadpool *pool)
 	}
 	ao2_ref(pool, +1);
 	ser->pool = pool;
+	ser->shutdown_group = ao2_bump(shutdown_group);
 	return ser;
 }
 
@@ -1187,6 +1296,10 @@ static int serializer_start(struct ast_taskprocessor_listener *listener)
 static void serializer_shutdown(struct ast_taskprocessor_listener *listener)
 {
 	struct serializer *ser = ast_taskprocessor_listener_get_user_data(listener);
+
+	if (ser->shutdown_group) {
+		serializer_shutdown_group_dec(ser->shutdown_group);
+	}
 	ao2_cleanup(ser);
 }
 
@@ -1201,27 +1314,35 @@ struct ast_taskprocessor *ast_threadpool_serializer_get_current(void)
 	return ast_threadstorage_get_ptr(&current_serializer);
 }
 
-struct ast_taskprocessor *ast_threadpool_serializer(const char *name, struct ast_threadpool *pool)
+struct ast_taskprocessor *ast_threadpool_serializer_group(const char *name,
+	struct ast_threadpool *pool, struct ast_serializer_shutdown_group *shutdown_group)
 {
-	RAII_VAR(struct serializer *, ser, NULL, ao2_cleanup);
-	RAII_VAR(struct ast_taskprocessor_listener *, listener, NULL, ao2_cleanup);
-	struct ast_taskprocessor *tps = NULL;
+	struct serializer *ser;
+	struct ast_taskprocessor_listener *listener;
+	struct ast_taskprocessor *tps;
 
-	ser = serializer_create(pool);
+	ser = serializer_create(pool, shutdown_group);
 	if (!ser) {
 		return NULL;
 	}
 
 	listener = ast_taskprocessor_listener_alloc(&serializer_tps_listener_callbacks, ser);
 	if (!listener) {
+		ao2_ref(ser, -1);
 		return NULL;
 	}
-	ser = NULL; /* ownership transferred to listener */
+	/* ser ref transferred to listener */
 
 	tps = ast_taskprocessor_create_with_listener(name, listener);
-	if (!tps) {
-		return NULL;
+	if (tps && shutdown_group) {
+		serializer_shutdown_group_inc(shutdown_group);
 	}
 
+	ao2_ref(listener, -1);
 	return tps;
 }
+
+struct ast_taskprocessor *ast_threadpool_serializer(const char *name, struct ast_threadpool *pool)
+{
+	return ast_threadpool_serializer_group(name, pool, NULL);
+}