[kernel] Add thead kobject class

Add the thread kernel API object and move the scheduler to use threads
instead of processes for scheduling and task switching.

src/kernel/objects/kobject.h

@@ -6,6 +6,8 @@
 #include "j6/types.h"
 #include "kutil/vector.h"
 
+class thread;
+
 /// Base type for all user-interactable kernel objects
 class kobject
 {
@@ -39,6 +41,9 @@ public:
 	/// \returns   The object type for the koid
 	static type koid_type(j6_koid_t koid);
 
+	/// Get this object's koid
+	inline j6_koid_t koid() const { return m_koid; }
+
 	/// Set the given signals active on this object
 	/// \arg s  The set of signals to assert
 	void assert_signal(j6_signal_t s);
@@ -47,31 +52,6 @@ public:
 	/// \arg s  The set of signals to deassert
 	void deassert_signal(j6_signal_t s);
 
-	class observer
-	{
-	public:
-		/// Callback for when signals change.
-		/// \arg obj     The object triggering the callback
-		/// \arg s       The current state of obj's signals
-		/// \arg ds      Which signals caused the callback
-		/// \arg result  Status code for this notification
-		/// \returns     True if this object wants to keep watching signals
-		virtual bool on_signals_changed(
-				kobject *obj,
-				j6_signal_t s,
-				j6_signal_t ds,
-				j6_status_t result) = 0;
-	};
-
-	/// Register a signal observer
-	/// \arg object  The observer
-	/// \arg s       The signals the object wants notifiations for
-	void register_signal_observer(observer *object, j6_signal_t s);
-
-	/// Deegister a signal observer
-	/// \arg object  The observer
-	void deregister_signal_observer(observer *object);
-
 	/// Increment the handle refcount
 	inline void handle_retain() { ++m_handle_count; }
 
@@ -80,31 +60,30 @@ public:
 		if (--m_handle_count == 0) on_no_handles();
 	}
 
+	/// Add the given thread to the list of threads waiting on this object.
+	inline void add_blocked_thread(thread *t) { m_blocked_threads.append(t); }
+
+	/// Remove the given thread from the list of threads waiting on this object.
+	inline void remove_blocked_thread(thread *t) { m_blocked_threads.remove_swap(t); }
+
 protected:
+	/// Interface for subclasses to handle when all handles are closed. Subclasses
+	/// should either call the base version, or assert j6_signal_no_handles.
+	virtual void on_no_handles();
+
+private:
 	kobject() = delete;
 	kobject(const kobject &other) = delete;
 	kobject(const kobject &&other) = delete;
 
 	/// Notifiy observers of this object
-	/// \arg mask    The signals that triggered this call. If 0, notify all observers.
 	/// \arg result  The result to pass to the observers
-	void notify_signal_observers(j6_signal_t mask, j6_status_t result = j6_status_ok);
-
-	/// Interface for subclasses to handle when all handles are closed. Subclasses
-	/// should either call the base version, or assert j6_signal_no_handles.
-	virtual void on_no_handles();
+	void notify_signal_observers();
 
 	j6_koid_t m_koid;
 	j6_signal_t m_signals;
 	uint16_t m_handle_count;
 
-	struct observer_registration
-	{
-		observer_registration(observer* o = nullptr, j6_signal_t s = 0) :
-			object(o), signals(s) {}
-
-		observer *object;
-		j6_signal_t signals;
-	};
-	kutil::vector<observer_registration> m_observers;
+protected:
+	kutil::vector<thread*> m_blocked_threads;
 };