event/TimeoutMonitor: eliminate support for periodic events

No caller needs this.  Fixes use-after-free after returning from
Client::OnTimeout().

src/ClientExpire.cxx

@@ -30,7 +30,7 @@ Client::SetExpired()
 	TimeoutMonitor::Schedule(0);
 }
 
-bool
+void
 Client::OnTimeout()
 {
 	if (!IsExpired()) {
@@ -39,5 +39,4 @@ Client::OnTimeout()
 	}
 
 	Close();
-	return false;
 }

src/ClientInternal.hxx

@@ -120,7 +120,7 @@ private:
 	virtual void OnSocketClosed() override;
 
 	/* virtual methods from class TimeoutMonitor */
-	virtual bool OnTimeout() override;
+	virtual void OnTimeout() override;
 };
 
 extern int client_timeout;

src/InotifyQueue.cxx

@@ -38,7 +38,7 @@ enum {
 	INOTIFY_UPDATE_DELAY_S = 5,
 };
 
-bool
+void
 InotifyQueue::OnTimeout()
 {
 	unsigned id;
@@ -47,17 +47,16 @@ InotifyQueue::OnTimeout()
 		const char *uri_utf8 = queue.front().c_str();
 
 		id = update_enqueue(uri_utf8, false);
-		if (id == 0)
+		if (id == 0) {
 			/* retry later */
-			return true;
+			ScheduleSeconds(INOTIFY_UPDATE_DELAY_S);
+			return;
+		}
 
 		g_debug("updating '%s' job=%u", uri_utf8, id);
 
 		queue.pop_front();
 	}
-
-	/* done, remove the timer event by returning false */
-	return false;
 }
 
 static bool

src/InotifyQueue.hxx

@@ -35,7 +35,7 @@ public:
 	void Enqueue(const char *uri_utf8);
 
 private:
-	virtual bool OnTimeout() override;
+	virtual void OnTimeout() override;
 };
 
 #endif

src/StateFile.cxx

@@ -116,9 +116,8 @@ StateFile::CheckModified()
 		ScheduleSeconds(2 * 60);
 }
 
-bool
+void
 StateFile::OnTimeout()
 {
 	Write();
-	return false;
 }

src/StateFile.hxx

@@ -67,7 +67,7 @@ private:
 	bool IsModified() const;
 
 	/* virtual methods from TimeoutMonitor */
-	virtual bool OnTimeout() override;
+	virtual void OnTimeout() override;
 };
 
 #endif /* STATE_FILE_H */

src/event/TimeoutMonitor.cxx

@@ -45,21 +45,17 @@ TimeoutMonitor::ScheduleSeconds(unsigned s)
 	source = loop.AddTimeoutSeconds(s, Callback, this);
 }
 
-bool
+void
 TimeoutMonitor::Run()
 {
-	bool result = OnTimeout();
-	if (!result && source != nullptr) {
-		g_source_unref(source);
-		source = nullptr;
-	}
-
-	return result;
+	Cancel();
+	OnTimeout();
 }
 
 gboolean
 TimeoutMonitor::Callback(gpointer data)
 {
 	TimeoutMonitor &monitor = *(TimeoutMonitor *)data;
-	return monitor.Run();
+	monitor.Run();
+	return false;
 }

src/event/TimeoutMonitor.hxx

@@ -47,13 +47,10 @@ public:
 	void Cancel();
 
 protected:
-	/**
-	 * @return true reschedules the timeout again
-	 */
-	virtual bool OnTimeout() = 0;
+	virtual void OnTimeout() = 0;
 
 private:
-	bool Run();
+	void Run();
 	static gboolean Callback(gpointer data);
 };