Rework DefaultNotificationService registration.

- Instead of implicitly registering and unregistering a service
  instance on construction/destruction, DefaultNotificationService
  now exports explicit Register()/Unregister() calls, which subclasses
  are expected to call when they're ready.

- Adjust all implementing subclasses. Resolves an issue with deadlocks
  when booting a DEBUG=1 build.

headers/private/kernel/Notifications.h

@@ -152,6 +152,9 @@ public:
 
 	virtual const char*			Name() { return fName; }
 
+			status_t			Register();
+			void				Unregister();
+
 protected:
 	virtual status_t			ToEventMask(const KMessage& eventSpecifier,
 									uint32& eventMask);

src/add-ons/kernel/network/notifications/notifications.cpp

@@ -130,22 +130,32 @@ notifications_std_ops(int32 op, ...)
 {
 	switch (op) {
 		case B_MODULE_INIT:
+		{
 			TRACE("init\n");
 
 			new(&sNotificationService) NetNotificationService();
+			status_t result = sNotificationService.Register();
+			if (result != B_OK)
+				return result;
 
 			register_generic_syscall(NET_NOTIFICATIONS_SYSCALLS,
 				net_notifications_control, 1, 0);
 			return B_OK;
-
+		}
 		case B_MODULE_UNINIT:
 			TRACE("uninit\n");
 
 			unregister_generic_syscall(NET_NOTIFICATIONS_SYSCALLS, 1);
 
+			// TODO: due to the way the locking in the notification
+			// manager works, there's a potential race condition here
+			// where someone attempts to add a listener right as
+			// we're uninitializing. Needs to be looked at/resolved.
+			sNotificationService.Unregister();
+
 			// we need to release the reference that was acquired
 			// on our behalf by the NotificationManager.
-//			sNotificationService.ReleaseReference();
+			sNotificationService.ReleaseReference();
 			sNotificationService.~NetNotificationService();
 			return B_OK;
 

src/system/kernel/Notifications.cpp

@@ -156,13 +156,11 @@ DefaultNotificationService::DefaultNotificationService(const char* name)
 	fName(name)
 {
 	recursive_lock_init(&fLock, name);
-	NotificationManager::Manager().RegisterService(*this);
 }
 
 
 DefaultNotificationService::~DefaultNotificationService()
 {
-	NotificationManager::Manager().UnregisterService(*this);
 	recursive_lock_destroy(&fLock);
 }
 
@@ -253,6 +251,20 @@ DefaultNotificationService::RemoveListener(const KMessage* eventSpecifier,
 }
 
 
+status_t
+DefaultNotificationService::Register()
+{
+	return NotificationManager::Manager().RegisterService(*this);
+}
+
+
+void
+DefaultNotificationService::Unregister()
+{
+	NotificationManager::Manager().UnregisterService(*this);
+}
+
+
 status_t
 DefaultNotificationService::ToEventMask(const KMessage& eventSpecifier,
 	uint32& eventMask)

src/system/kernel/device_manager/IOSchedulerRoster.cpp

@@ -78,10 +78,12 @@ IOSchedulerRoster::IOSchedulerRoster()
 	fNotificationService("I/O")
 {
 	mutex_init(&fLock, "IOSchedulerRoster");
+	fNotificationService.Register();
 }
 
 
 IOSchedulerRoster::~IOSchedulerRoster()
 {
 	mutex_destroy(&fLock);
+	fNotificationService.Unregister();
 }

src/system/kernel/disk_device_manager/KDiskDeviceManager.cpp

@@ -254,6 +254,8 @@ KDiskDeviceManager::KDiskDeviceManager()
 	if (InitCheck() != B_OK)
 		return;
 
+	fNotifications->Register();
+
 	RescanDiskSystems();
 
 	fMediaChecker = spawn_kernel_thread(_CheckMediaStatusDaemon,
@@ -310,6 +312,8 @@ KDiskDeviceManager::~KDiskDeviceManager()
 			delete diskSystem;
 	}
 
+	fNotifications->Unregister();
+
 	// delete the containers
 	delete fPartitions;
 	delete fDevices;

src/system/kernel/image.cpp

@@ -343,6 +343,8 @@ image_init(void)
 
 	new(&sNotificationService) ImageNotificationService();
 
+	sNotificationService.Register();
+
 #ifdef ADD_DEBUGGER_COMMANDS
 	add_debugger_command("team_images", &dump_images_list, "Dump all registered images from the current team");
 #endif

src/system/kernel/port.cpp

@@ -792,6 +792,7 @@ port_init(kernel_args *args)
 		"  <condition> - address of the port's read or write condition.\n", 0);
 
 	new(&sNotificationService) PortNotificationService();
+	sNotificationService.Register();
 	sPortsActive = true;
 	return B_OK;
 }

src/system/kernel/team.cpp

@@ -2771,6 +2771,8 @@ team_init(kernel_args* args)
 
 	new(&sNotificationService) TeamNotificationService();
 
+	sNotificationService.Register();
+
 	return B_OK;
 }
 

src/system/kernel/thread.cpp

@@ -2738,6 +2738,8 @@ thread_init(kernel_args *args)
 	// init the notification service
 	new(&sNotificationService) ThreadNotificationService();
 
+	sNotificationService.Register();
+
 	// start the undertaker thread
 	new(&sUndertakerEntries) DoublyLinkedList<UndertakerEntry>();
 	sUndertakerCondition.Init(&sUndertakerEntries, "undertaker entries");