event/SocketMonitor: add method Abandon()

src/event/Loop.cxx

@@ -58,13 +58,18 @@ EventLoop::Break()
 		AddCall([this]() { Break(); });
 }
 
-bool
-EventLoop::RemoveFD(int _fd, SocketMonitor &m)
+void
+EventLoop::Abandon(SocketMonitor &m)
 {
 	for (unsigned i = 0, n = n_events; i < n; ++i)
 		if (events[i].data.ptr == &m)
 			events[i].events = 0;
+}
 
+bool
+EventLoop::RemoveFD(int _fd, SocketMonitor &m)
+{
+	Abandon(m);
 	return epoll.Remove(_fd);
 }
 

src/event/Loop.hxx

@@ -121,6 +121,13 @@ public:
 		return epoll.Modify(_fd, flags, &m);
 	}
 
+	/**
+	 * Remove the given #SocketMonitor after the file descriptor
+	 * has been closed.  This is like RemoveFD(), but does not
+	 * attempt to use #EPOLL_CTL_DEL.
+	 */
+	void Abandon(SocketMonitor &m);
+
 	bool RemoveFD(int fd, SocketMonitor &m);
 
 	void AddIdle(IdleMonitor &i);

src/event/SocketMonitor.cxx

@@ -152,6 +152,19 @@ SocketMonitor::Steal()
 }
 
 void
+SocketMonitor::Abandon()
+{
+	assert(IsDefined());
+
+#ifdef USE_EPOLL
+	fd = -1;
+	loop.Abandon(*this);
+#else
+	Steal();
+#endif
+}
+
+void
 SocketMonitor::Close()
 {
 	close_socket(Steal());

src/event/SocketMonitor.hxx

@@ -118,6 +118,11 @@ public:
 	 */
 	int Steal();
 
+	/**
+	 * Somebody has closed the socket.  Unregister this object.
+	 */
+	void Abandon();
+
 	void Close();
 
 	unsigned GetScheduledFlags() const {