bombshell-client gains a lock that prevents it from hanging if two parallel requests happen too fast

bin/bombshell-client

@@ -1,6 +1,7 @@
 #!/usr/bin/python -u
 
 import cPickle
+import contextlib
 import fcntl
 import os
 import pipes
@@ -13,6 +14,18 @@ import sys
 import threading
 
 
+@contextlib.contextmanager
+def mutexfile(filepath):
+    oldumask = os.umask(0077)
+    try:
+        f = file(filepath, "a")
+    finally:
+        os.umask(oldumask)
+    fcntl.lockf(f.fileno(), fcntl.LOCK_EX)
+    yield
+    f.close()
+
+
 debug_lock = threading.Lock()
 debug_enabled = False
 class LoggingEmu():
@@ -250,6 +263,7 @@ def main_master():
 
   saved_stderr = os.fdopen(os.dup(sys.stderr.fileno()), "a")
 
+  with mutexfile(os.path.expanduser("~/.bombshell-lock")):
       try:
         p = subprocess.Popen(
           ["qrexec-client-vm", remote_vm, "qubes.VMShell"],