From c64e0c0e64a0355f0813b96a6a2a4a6701d6684d Mon Sep 17 00:00:00 2001
From: Neil Booth <kyuupichan@gmail.com>
Date: Tue, 5 May 2015 18:40:22 +0900
Subject: [PATCH] Send requests only from the interface thread.

Currently requests are sent from the requestor's thread.  The lock is
not properly held where necessary so this is not thread-safe.  For example
it can race with the thread stopping and closing the socket the
requestor is trying to use to send with.

Resolve such races by having send_request() simply queue the requests,
which are asynchronously sent from the interface thread itself.
---
 lib/interface.py | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/lib/interface.py b/lib/interface.py
index ffdb3d68c..986ab3fc8 100644
--- a/lib/interface.py
+++ b/lib/interface.py
@@ -60,6 +60,7 @@ class TcpInterface(threading.Thread):
         self.debug = False # dump network messages. can be changed at runtime using the console
         self.message_id = 0
         self.response_queue = response_queue
+        self.request_queue = Queue.Queue()
         self.unanswered_requests = {}
         # are we waiting for a pong?
         self.is_ping = False
@@ -249,22 +250,26 @@ class TcpInterface(threading.Thread):
 
         return s
 
+    def send_request(self, request, response_queue = None):
+        '''Queue a request.  Blocking only if called from other threads.'''
+        self.request_queue.put((request, response_queue), threading.current_thread() != self)
 
-    def send_request(self, request, queue=None):
-        _id = request.get('id')
-        method = request.get('method')
-        params = request.get('params')
-        with self.lock:
+    def send_requests(self):
+        '''Sends all queued requests'''
+        while self.is_connected() and not self.request_queue.empty():
+            request, response_queue = self.request_queue.get()
+            method = request.get('method')
+            params = request.get('params')
+            r = {'id': self.message_id, 'method': method, 'params': params}
             try:
-                r = {'id':self.message_id, 'method':method, 'params':params}
                 self.pipe.send(r)
-                if self.debug:
-                    self.print_error("-->", r)
             except socket.error, e:
-                self.print_error("socked error:", e)
+                self.print_error("socket error:", e)
                 self.connected = False
                 return
-            self.unanswered_requests[self.message_id] = method, params, _id, queue
+            if self.debug:
+                self.print_error("-->", r)
+            self.unanswered_requests[self.message_id] = method, params, request.get('id'), response_queue
             self.message_id += 1
 
     def is_connected(self):
@@ -304,6 +309,7 @@ class TcpInterface(threading.Thread):
         request_time = False
         while self.connected:
             self.maybe_ping()
+            self.send_requests()
             if not self.connected:
                 break
             try: