Changing semantics of thread stop methods.

PrepareStop() is now SignalStop() and just signals a thread that it
should terminate. After that's called, WaitForStop() (formerly Stop())
wait for it to actually finish processing.

When stopping writers during operation, we now no longer wait for them
to finish.

src/threading/BasicThread.h

@@ -71,32 +71,33 @@ public:
 	void Start();
 
 	/**
-	 * Signals the thread to prepare for stopping. This must be called
-	 * before Stop() and allows the thread to trigger shutting down
-	 * without yet blocking for doing so.
+	 * Signals the thread to prepare for stopping, but doesn't block to
+	 * wait for that to happen. Use WaitForStop() for that.
 	 *
+	 * The method lets Terminating() now return true, it does however not
+	 * force the thread to terminate. It's up to the Run() method to to
+	 * query Terminating() and exit eventually.
+	 * 
 	 * Calling this method has no effect if Start() hasn't been executed
 	 * yet.
 	 *
 	 * Only Bro's main thread must call this method.
 	 */
-	void PrepareStop();
+	void SignalStop();
 
 	/**
-	 * Signals the thread to stop. The method lets Terminating() now
-	 * return true. It does however not force the thread to terminate.
-	 * It's up to the Run() method to to query Terminating() and exit
-	 * eventually.
+	 * Waits until a thread has stopped after receiving SignalStop().
 	 *
 	 * Calling this method has no effect if Start() hasn't been executed
-	 * yet.
+	 * yet. If this is executed without calling SignalStop() first,
+	 * results are undefined.
 	 *
 	 * Only Bro's main thread must call this method.
 	 */
-	void Stop();
+	void WaitForStop();
 
 	/**
-	 * Returns true if Stop() has been called.
+	 * Returns true if WaitForStop() has been called and finished.
 	 *
 	 * This method is safe to call from any thread.
 	 */
@@ -145,18 +146,19 @@ protected:
 	virtual void OnStart()	{}
 
 	/**
-	 * Executed with PrepareStop() (and before OnStop()). This is a hook
-	 * into preparing the thread for stopping. It will be called from
-	 * Bro's main thread before the thread has been signaled to stop.
+	 * Executed with SignalStop(). This is a hook into preparing the
+	 * thread for stopping. It will be called from Bro's main thread
+	 * before the thread has been signaled to stop.
 	 */
-	virtual void OnPrepareStop()	{}
+	virtual void OnSignalStop()	{}
 
 	/**
-	 * Executed with Stop() (and after OnPrepareStop()). This is a hook
-	 * into stopping the thread. It will be called from Bro's main thread
-	 * after the thread has been signaled to stop.
+	 * Executed with WaitForStop(). This is a hook into waiting for the
+	 * thread to stop. It must be overridden by derived classes and only
+	 * return once the thread has indeed finished processing. The method
+	 * will be called from Bro's main thread.
 	 */
-	virtual void OnStop()	{}
+	virtual void OnWaitForStop() = 0;
 
 	/**
 	 * Executed with Kill(). This is a hook into killing the thread.