add lock to stdin

Author: Quentin Peter

ipykernel/kernelapp.py

@@ -448,7 +448,6 @@ def init_kernel(self):
                                 user_ns=self.user_ns,
         )
         kernel.stdin_stream = stdin_stream
-        kernel._stdin_msg = None
 
         def handle_msg(msg):
             idents, msg = self.session.feed_identities(msg, copy=False)

ipykernel/kernelbase.py

@@ -172,6 +172,9 @@ def __init__(self, **kwargs):
         for msg_type in self.control_msg_types:
             self.control_handlers[msg_type] = getattr(self, msg_type)
 
+        self._stdin_msg = None
+        self._stdin_lock = threading.Lock()
+
     @gen.coroutine
     def dispatch_control(self, msg):
         """dispatch control requests"""
@@ -876,13 +879,14 @@ def _input_request(self, prompt, ident, parent, password=False):
                 else:
                     raise
 
-        self._stdin_msg = None
-        # Send the input request.
-        content = json_clean(dict(prompt=prompt, password=password))
-        self.session.send(self.stdin_socket, u'input_request', content, parent,
-                          ident=ident)
-        # Await a response.
-        reply = self._wait_input_request_reply()
+        with self._stdin_lock:
+            self._stdin_msg = None
+            # Send the input request.
+            content = json_clean(dict(prompt=prompt, password=password))
+            self.session.send(self.stdin_socket, u'input_request', content, parent,
+                              ident=ident)
+            # Await a response.
+            reply = self._wait_input_request_reply()
 
         try:
             value = py3compat.unicode_to_str(reply['content']['value'])