res_pjsip_exten_state,res_pjsip_mwi: Allow unload on shutdown

Commit f66f77f last year prevents the res_pjsip_exten_state and
res_pjsip_mwi modules from unloading due to possible pjproject
asserts if the modules are reloaded. A side effect of the
implementation is that the taskprocessors these modules use aren't
being released. When asterisk is doing a graceful shutdown, it
waits AST_TASKPROCESSOR_SHUTDOWN_MAX_WAIT seconds for all
taskprocessors to stop but since those 2 modules don't release
theirs, the shutdown hangs for that amount of time.

This change allows the modules to be unloaded and their resources to
be released when ast_shutdown_final is true.

Resolves: #379
(cherry picked from commit b9ee664440)

res/res_pjsip_exten_state.c

@@ -973,7 +973,18 @@ static int publisher_stop(struct ast_sip_outbound_publish_client *client)
 
 static int unload_module(void)
 {
-#if 0
+	/*
+	 * pjsip_evsub_register_pkg is called by ast_sip_register_subscription_handler
+	 * but there is no corresponding unregister function, so unloading
+	 * a module does not remove the event package. If this module is ever
+	 * loaded again, then pjproject will assert and cause a crash.
+	 * For that reason, we must only be allowed to unload when
+	 * asterisk is shutting down.  If a pjsip_evsub_unregister_pkg
+	 * API is added in the future then we should go back to unloading
+	 * the module as intended.
+	 */
+
+	if (ast_shutdown_final()) {
 		ast_sip_unregister_event_publisher_handler(&dialog_publisher);
 		ast_sip_unregister_subscription_handler(&dialog_handler);
 		ast_sip_unregister_event_publisher_handler(&presence_publisher);
@@ -988,18 +999,9 @@ static int unload_module(void)
 		publishers = NULL;
 
 		return 0;
-#else
-	/* If we were allowed to unload, the above is what we would do.
-	 * pjsip_evsub_register_pkg is called by ast_sip_register_subscription_handler
-	 * but there is no corresponding unregister function, so unloading
-	 * a module does not remove the event package. If this module is ever
-	 * loaded again, then pjproject will assert and cause a crash.
-	 * For that reason, we must not be allowed to unload, but if
-	 * a pjsip_evsub_unregister_pkg API is added in the future
-	 * then we should go back to unloading the module as intended.
-	 */
+	} else {
 		return -1;
-#endif
+	}
 }
 
 static int load_module(void)

res/res_pjsip_mwi.c

@@ -1524,7 +1524,18 @@ static int reload(void)
 
 static int unload_module(void)
 {
-#if 0
+	/*
+	 * pjsip_evsub_register_pkg is called by ast_sip_register_subscription_handler
+	 * but there is no corresponding unregister function, so unloading
+	 * a module does not remove the event package. If this module is ever
+	 * loaded again, then pjproject will assert and cause a crash.
+	 * For that reason, we must only be allowed to unload when
+	 * asterisk is shutting down.  If a pjsip_evsub_unregister_pkg
+	 * API is added in the future then we should go back to unloading
+	 * the module as intended.
+	 */
+
+	if (ast_shutdown_final()) {
 		struct ao2_container *unsolicited_mwi;
 
 		ast_sorcery_observer_remove(ast_sip_get_sorcery(), "global", &global_observer);
@@ -1549,18 +1560,9 @@ static int unload_module(void)
 		ast_free(default_voicemail_extension);
 		default_voicemail_extension = NULL;
 		return 0;
-#else
-	/* If we were allowed to unload, the above is what we would do.
-	 * pjsip_evsub_register_pkg is called by ast_sip_register_subscription_handler
-	 * but there is no corresponding unregister function, so unloading
-	 * a module does not remove the event package. If this module is ever
-	 * loaded again, then pjproject will assert and cause a crash.
-	 * For that reason, we must not be allowed to unload, but if
-	 * a pjsip_evsub_unregister_pkg API is added in the future
-	 * then we should go back to unloading the module as intended.
-	 */
+	} else {
 		return -1;
-#endif
+	}
 }
 
 static int load_module(void)