fix a deadlock when the client disconnects while flushing data

Author: mmerickel

waitress/channel.py

@@ -151,7 +151,7 @@ def handle_write(self):
             self.will_close = True
 
         if self.will_close:
-            self.handle_close()
+            self.handle_close(lock=False)
 
     def readable(self):
         # We might want to create a new task.  We can only do this if:
@@ -168,7 +168,7 @@ def handle_read(self):
         except socket.error:
             if self.adj.log_socket_errors:
                 self.logger.exception('Socket error')
-            self.handle_close()
+            self.handle_close(lock=True)
             return
         if data:
             self.last_activity = time.time()
@@ -274,17 +274,21 @@ def _flush_some(self):
 
         return False
 
-    def handle_close(self):
-        # avoid closing the outbufs while a task is potentially adding data
-        # to them in write_soon
-        with self.outbuf_lock:
+    def handle_close(self, lock=True):
+        # NB: default to True for when asyncore calls this function directly
+        if lock:
+            self.outbuf_lock.acquire()
+        try:
             for outbuf in self.outbufs:
                 try:
                     outbuf.close()
                 except:
                     self.logger.exception(
                         'Unknown exception while trying to close outbuf')
             self.connected = False
+        finally:
+            if lock:
+                self.outbuf_lock.release()
         wasyncore.dispatcher.close(self)
 
     def add_channel(self, map=None):