Implemented a generic system watching mechanism with a userland API. Currently

only a few events can be watched (team creation/deletion/exec, thread creation/
deletion/name changes). The functions start_system_watching()/
stop_system_watching start/stop watching events.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@39862 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/ksystem_info.h

@@ -8,6 +8,7 @@
 
 #include <OS.h>
 
+
 struct kernel_args;
 
 
@@ -15,15 +16,24 @@ struct kernel_args;
 extern "C" {
 #endif
 
-extern status_t system_info_init(struct kernel_args *args);
-extern uint32 get_haiku_revision(void);
 
-extern status_t _user_get_system_info(system_info *userInfo, size_t size);
+status_t system_info_init(struct kernel_args *args);
-extern status_t _user_get_system_info_etc(int32 id, void *buffer,
+status_t system_notifications_init();
-	size_t bufferSize);
+uint32 get_haiku_revision(void);
+
+status_t _user_get_system_info(system_info *userInfo, size_t size);
+status_t _user_get_system_info_etc(int32 id, void *buffer,
+			size_t bufferSize);
+
+status_t _user_start_system_watching(int32 object, uint32 flags,
+			port_id port, int32 token);
+status_t _user_stop_system_watching(int32 object, uint32 flags,
+			port_id port, int32 token);
+
 
 #ifdef __cplusplus
 }
 #endif
 
+
 #endif	/* _KERNEL_SYSTEM_INFO_H */

headers/private/system/syscalls.h

@@ -174,6 +174,11 @@ extern status_t		_kern_get_team_usage_info(team_id team, int32 who,
 extern status_t		_kern_get_extended_team_info(team_id teamID, uint32 flags,
 						void* buffer, size_t size, size_t* _sizeNeeded);
 
+extern status_t		_kern_start_system_watching(int32 object, uint32 flags,
+						port_id port, int32 token);
+extern status_t		_kern_stop_system_watching(int32 object, uint32 flags,
+						port_id port, int32 token);
+
 extern status_t		_kern_block_thread(uint32 flags, bigtime_t timeout);
 extern status_t		_kern_unblock_thread(thread_id thread, status_t status);
 extern status_t		_kern_unblock_threads(thread_id* threads, uint32 count,

headers/private/system/system_info.h

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008 Haiku, Inc. All rights reserved.
+ * Copyright 2008-2010, Haiku, Inc. All rights reserved.
  * Distributed under the terms of the MIT License.
  */
 #ifndef _SYSTEM_INFO_H
@@ -24,14 +24,56 @@ struct system_memory_info {
 };
 
 
+enum {
+	// team creation or deletion; object == -1; either one also triggers on
+	// exec()
+	B_WATCH_SYSTEM_TEAM_CREATION		= 0x01,
+	B_WATCH_SYSTEM_TEAM_DELETION		= 0x02,
+
+	// thread creation or deletion or property (name, priority) changes;
+	// object == team ID or -1 for all teams
+	B_WATCH_SYSTEM_THREAD_CREATION		= 0x04,
+	B_WATCH_SYSTEM_THREAD_DELETION		= 0x08,
+	B_WATCH_SYSTEM_THREAD_PROPERTIES	= 0x10,
+
+	B_WATCH_SYSTEM_ALL
+		= B_WATCH_SYSTEM_TEAM_CREATION
+		| B_WATCH_SYSTEM_TEAM_DELETION
+		| B_WATCH_SYSTEM_THREAD_CREATION
+		| B_WATCH_SYSTEM_THREAD_DELETION
+		| B_WATCH_SYSTEM_THREAD_PROPERTIES
+};
+
+enum {
+	// message what for the notification messages
+	B_SYSTEM_OBJECT_UPDATE				= 'SOUP',
+
+	// "opcode" values
+	B_TEAM_CREATED						= 0,
+	B_TEAM_DELETED						= 1,
+	B_TEAM_EXEC							= 2,
+	B_THREAD_CREATED					= 3,
+	B_THREAD_DELETED					= 4,
+	B_THREAD_NAME_CHANGED				= 5
+};
+
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-extern status_t get_system_info_etc(int32 id, void *buffer, size_t bufferSize);
+
+status_t get_system_info_etc(int32 id, void* buffer, size_t bufferSize);
+
+status_t start_system_watching(int32 object, uint32 flags, port_id port,
+			int32 token);
+status_t stop_system_watching(int32 object, uint32 flags, port_id port,
+			int32 token);
+
 
 #ifdef __cplusplus
 }
 #endif
 
+
 #endif	/* _SYSTEM_INFO_H */

src/system/kernel/main.cpp

@@ -270,6 +270,9 @@ main2(void *unused)
 	TRACE("init user mutex\n");
 	user_mutex_init();
 
+	TRACE("init system notifications\n");
+	system_notifications_init();
+
 	TRACE("Init modules\n");
 	boot_splash_set_stage(BOOT_SPLASH_STAGE_1_INIT_MODULES);
 	module_init_post_threads();

src/system/kernel/system_info.cpp

@@ -5,6 +5,7 @@
  * Authors:
  *		Stefano Ceccherini
  *		Axel Dörfler, [email protected]
+ *		Ingo Weinhold, [email protected]
  */
 
 
@@ -17,16 +18,22 @@
 #include <OS.h>
 #include <KernelExport.h>
 
+#include <AutoDeleter.h>
+
 #include <block_cache.h>
 #include <cpu.h>
 #include <debug.h>
 #include <kernel.h>
+#include <lock.h>
+#include <Notifications.h>
+#include <messaging.h>
 #include <port.h>
 #include <real_time_clock.h>
 #include <sem.h>
 #include <smp.h>
 #include <team.h>
 #include <thread.h>
+#include <util/AutoLock.h>
 #include <vm/vm.h>
 #include <vm/vm_page.h>
 
@@ -66,6 +73,335 @@ dump_info(int argc, char **argv)
 }
 
 
+//	#pragma mark - user notifications
+
+
+class SystemNotificationService : private NotificationListener {
+public:
+	SystemNotificationService()
+	{
+		mutex_init(&fLock, "system notification service");
+	}
+
+	status_t Init()
+	{
+		status_t error = fTeamListeners.Init();
+		if (error != B_OK)
+			return error;
+
+		error = NotificationManager::Manager().AddListener("teams",
+			TEAM_ADDED | TEAM_REMOVED | TEAM_EXEC, *this);
+		if (error != B_OK)
+			return error;
+
+		error = NotificationManager::Manager().AddListener("threads",
+			THREAD_ADDED | THREAD_REMOVED | TEAM_EXEC, *this);
+		if (error != B_OK)
+			return error;
+
+		return B_OK;
+	}
+
+	status_t StartListening(int32 object, uint32 flags, port_id port,
+		int32 token)
+	{
+		// check the parameters
+		if ((object < 0 && object != -1) || port < 0)
+			return B_BAD_VALUE;
+
+		if ((flags & B_WATCH_SYSTEM_ALL) == 0
+			|| (flags & ~(uint32)B_WATCH_SYSTEM_ALL) != 0) {
+			return B_BAD_VALUE;
+		}
+
+		MutexLocker locker(fLock);
+
+		// maybe the listener already exists
+		ListenerList* listenerList;
+		Listener* listener = _FindListener(object, port, token, listenerList);
+		if (listener != NULL) {
+			// just add the new flags
+			listener->flags |= flags;
+			return B_OK;
+		}
+
+		// create a new listener
+		listener = new(std::nothrow) Listener;
+		if (listener == NULL)
+			return B_NO_MEMORY;
+		ObjectDeleter<Listener> listenerDeleter(listener);
+
+		listener->port = port;
+		listener->token = token;
+		listener->flags = flags;
+
+		// if there's no list yet, create a new list
+		if (listenerList == NULL) {
+			listenerList = new(std::nothrow) ListenerList;
+			if (listenerList == NULL)
+				return B_NO_MEMORY;
+
+			listenerList->object = object;
+
+			fTeamListeners.Insert(listenerList);
+		}
+
+		listener->list = listenerList;
+		listenerList->listeners.Add(listener);
+		listenerDeleter.Detach();
+
+		team_associate_data(listener);
+
+		return B_OK;
+	}
+
+	status_t StopListening(int32 object, uint32 flags, port_id port,
+		int32 token)
+	{
+		MutexLocker locker(fLock);
+
+		// find the listener
+		ListenerList* listenerList;
+		Listener* listener = _FindListener(object, port, token, listenerList);
+		if (listener == NULL)
+			return B_ENTRY_NOT_FOUND;
+
+		// clear the given flags
+		listener->flags &= ~flags;
+
+		if (listener->flags != 0)
+			return B_OK;
+
+		team_dissociate_data(listener);
+		_RemoveListener(listener);
+
+		return B_OK;
+	}
+
+private:
+	struct ListenerList;
+
+	struct Listener : AssociatedData {
+		DoublyLinkedListLink<Listener>	listLink;
+		ListenerList*					list;
+		port_id							port;
+		int32							token;
+		uint32							flags;
+
+		virtual void OwnerDeleted(AssociatedDataOwner* owner);
+	};
+
+	friend struct Listener;
+
+	struct ListenerList {
+		typedef DoublyLinkedList<Listener,
+			DoublyLinkedListMemberGetLink<Listener, &Listener::listLink> > List;
+
+		ListenerList*	hashNext;
+		List			listeners;
+		int32			object;
+	};
+
+	struct ListenerHashDefinition {
+		typedef int32			KeyType;
+		typedef	ListenerList	ValueType;
+
+		size_t HashKey(int32 key) const
+		{
+			return key;
+		}
+
+		size_t Hash(const ListenerList* value) const
+		{
+			return HashKey(value->object);
+		}
+
+		bool Compare(int32 key, const ListenerList* value) const
+		{
+			return value->object == key;
+		}
+
+		ListenerList*& GetLink(ListenerList* value) const
+		{
+			return value->hashNext;
+		}
+	};
+
+	typedef BOpenHashTable<ListenerHashDefinition> ListenerHash;
+
+private:
+	virtual void EventOccurred(NotificationService& service,
+		const KMessage* event)
+	{
+		MutexLocker locker(fLock);
+
+		int32 eventCode;
+		int32 teamID;
+		if (event->FindInt32("event", &eventCode) != B_OK
+			|| event->FindInt32("team", &teamID) != B_OK) {
+			return;
+		}
+
+		int32 object;
+		uint32 opcode;
+		uint32 flags;
+
+		// translate the event
+		if (event->What() == TEAM_MONITOR) {
+			switch (eventCode) {
+				case TEAM_ADDED:
+					opcode = B_TEAM_CREATED;
+					flags = B_WATCH_SYSTEM_TEAM_CREATION;
+					break;
+				case TEAM_REMOVED:
+					opcode = B_TEAM_DELETED;
+					flags = B_WATCH_SYSTEM_TEAM_DELETION;
+					break;
+				case TEAM_EXEC:
+					opcode = B_TEAM_EXEC;
+					flags = B_WATCH_SYSTEM_TEAM_CREATION
+						| B_WATCH_SYSTEM_TEAM_DELETION;
+					break;
+				default:
+					return;
+			}
+
+			object = teamID;
+		} else if (event->What() == THREAD_MONITOR) {
+			if (event->FindInt32("thread", &object) != B_OK)
+				return;
+
+			switch (eventCode) {
+				case THREAD_ADDED:
+					opcode = B_THREAD_CREATED;
+					flags = B_WATCH_SYSTEM_THREAD_CREATION;
+					break;
+				case THREAD_REMOVED:
+					opcode = B_THREAD_DELETED;
+					flags = B_WATCH_SYSTEM_THREAD_DELETION;
+					break;
+				case THREAD_NAME_CHANGED:
+					opcode = B_THREAD_NAME_CHANGED;
+					flags = B_WATCH_SYSTEM_THREAD_PROPERTIES;
+					break;
+				default:
+					return;
+			}
+		} else
+			return;
+
+		// find matching listeners
+		messaging_target targets[kMaxMessagingTargetCount];
+		int32 targetCount = 0;
+
+		_AddTargets(fTeamListeners.Lookup(teamID), flags, targets,
+			targetCount, object, opcode);
+		_AddTargets(fTeamListeners.Lookup(-1), flags, targets, targetCount,
+			object, opcode);
+
+		// send the message
+		if (targetCount > 0)
+			_SendMessage(targets, targetCount, teamID, opcode);
+	}
+
+	void _AddTargets(ListenerList* listenerList, uint32 flags,
+		messaging_target* targets, int32& targetCount, int32 object,
+		uint32 opcode)
+	{
+		if (listenerList == NULL)
+			return;
+
+		for (ListenerList::List::Iterator it
+				= listenerList->listeners.GetIterator();
+			Listener* listener = it.Next();) {
+			if ((listener->flags & flags) == 0)
+				continue;
+
+			// array is full -- need to flush it first
+			if (targetCount == kMaxMessagingTargetCount) {
+				_SendMessage(targets, targetCount, object, opcode);
+				targetCount = 0;
+			}
+
+			// add the listener
+			targets[targetCount].port = listener->port;
+			targets[targetCount++].token = listener->token;
+		}
+	}
+
+	void _SendMessage(messaging_target* targets, int32 targetCount,
+		int32 object, uint32 opcode)
+	{
+		// prepare the message
+		char buffer[128];
+		KMessage message;
+		message.SetTo(buffer, sizeof(buffer), B_SYSTEM_OBJECT_UPDATE);
+		message.AddInt32("opcode", opcode);
+		if (opcode < B_THREAD_CREATED)
+			message.AddInt32("team", object);
+		else
+			message.AddInt32("thread", object);
+
+		// send it
+		send_message(message.Buffer(), message.ContentSize(), targets,
+			targetCount);
+	}
+
+	Listener* _FindListener(int32 object, port_id port, int32 token,
+		ListenerList*& _listenerList)
+	{
+		_listenerList = fTeamListeners.Lookup(object);
+		if (_listenerList == NULL)
+			return NULL;
+
+		for (ListenerList::List::Iterator it
+				= _listenerList->listeners.GetIterator();
+			Listener* listener = it.Next();) {
+			if (listener->port == port && listener->token == token)
+				return listener;
+		}
+
+		return NULL;
+	}
+
+	void _RemoveObsoleteListener(Listener* listener)
+	{
+		MutexLocker locker(fLock);
+		_RemoveListener(listener);
+	}
+
+	void _RemoveListener(Listener* listener)
+	{
+		// no flags anymore -- remove the listener
+		ListenerList* listenerList = listener->list;
+		listenerList->listeners.Remove(listener);
+		listener->ReleaseReference();
+
+		if (listenerList->listeners.IsEmpty()) {
+			// no listeners in the list anymore -- remove the list from the hash
+			// table
+			fTeamListeners.Remove(listenerList);
+			delete listenerList;
+		}
+	}
+
+private:
+	static const int32 kMaxMessagingTargetCount = 8;
+
+	mutex			fLock;
+	ListenerHash	fTeamListeners;
+};
+
+static SystemNotificationService sSystemNotificationService;
+
+
+void
+SystemNotificationService::Listener::OwnerDeleted(AssociatedDataOwner* owner)
+{
+	sSystemNotificationService._RemoveObsoleteListener(this);
+}
+
+
 //	#pragma mark -
 
 
@@ -115,6 +451,21 @@ system_info_init(struct kernel_args *args)
 }
 
 
+status_t
+system_notifications_init()
+{
+	new (&sSystemNotificationService) SystemNotificationService;
+
+	status_t error = sSystemNotificationService.Init();
+	if (error != B_OK) {
+		panic("system_info_init(): Failed to init system notification service");
+		return error;
+	}
+
+	return B_OK;
+}
+
+
 uint32
 get_haiku_revision(void)
 {
@@ -170,3 +521,20 @@ _user_get_system_info_etc(int32 id, void* userInfo, size_t size)
 			return B_BAD_VALUE;
 	}
 }
+
+
+status_t
+_user_start_system_watching(int32 object, uint32 flags, port_id port,
+	int32 token)
+{
+	return sSystemNotificationService.StartListening(object, flags, port,
+		token);
+}
+
+
+status_t
+_user_stop_system_watching(int32 object, uint32 flags, port_id port,
+	int32 token)
+{
+	return sSystemNotificationService.StopListening(object, flags, port, token);
+}

src/system/libroot/os/system_info.c

@@ -30,6 +30,20 @@ get_system_info_etc(int32 id, void *info, size_t size)
 }
 
 
+status_t
+start_system_watching(int32 object, uint32 flags, port_id port, int32 token)
+{
+	return _kern_start_system_watching(object, flags, port, token);
+}
+
+
+status_t
+stop_system_watching(int32 object, uint32 flags, port_id port, int32 token)
+{
+	return _kern_stop_system_watching(object, flags, port, token);
+}
+
+
 int32
 is_computer_on(void)
 {