Do threading.Lock the Right Way.

git_cache.py

 #!/usr/bin/env python
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """A git command for managing a local cache of git repositories."""
 
 from __future__ import print_function
 import errno
 import logging
@@ skipping 182 matching lines @@
         return target
       if sys.platform.startswith('win'):
         for suffix in ('.bat', '.cmd', '.exe'):
           alt_target = target + suffix
           if os.path.isfile(alt_target) and os.access(alt_target, os.X_OK):
             return alt_target
     return None
 
   @classmethod
   def SetCachePath(cls, cachepath):
-    cls.cachepath_lock.acquire()
-    setattr(cls, 'cachepath', cachepath)
-    cls.cachepath_lock.release()
+    with cls.cachepath_lock:
+      setattr(cls, 'cachepath', cachepath)
 
   @classmethod
   def GetCachePath(cls):
-    cls.cachepath_lock.acquire()
-    if not hasattr(cls, 'cachepath'):
-      try:
-        cachepath = subprocess.check_output(
-            [cls.git_exe, 'config', '--global', 'cache.cachepath']).strip()
-      except subprocess.CalledProcessError:
-        cachepath = None
-      if not cachepath:
-        cls.cachepath_lock.release()
-        raise RuntimeError('No global cache.cachepath git configuration found.')
-      setattr(cls, 'cachepath', cachepath)
-    cls.cachepath_lock.release()
-    return getattr(cls, 'cachepath')
+    with cls.cachepath_lock:
+      if not hasattr(cls, 'cachepath'):
+        try:
+          cachepath = subprocess.check_output(
+              [cls.git_exe, 'config', '--global', 'cache.cachepath']).strip()
+        except subprocess.CalledProcessError:
+          cachepath = None
+        if not cachepath:
+          raise RuntimeError(
+              'No global cache.cachepath git configuration found.')
+        setattr(cls, 'cachepath', cachepath)
+      return getattr(cls, 'cachepath')
 
   def RunGit(self, cmd, **kwargs):
     """Run git in a subprocess."""
     cwd = kwargs.setdefault('cwd', self.mirror_path)
     kwargs.setdefault('print_stdout', False)
     kwargs.setdefault('filter_fn', self.print)
     env = kwargs.get('env') or kwargs.setdefault('env', os.environ.copy())
     env.setdefault('GIT_ASKPASS', 'true')
     env.setdefault('SSH_ASKPASS', 'true')
     self.print('running "git %s" in "%s"' % (' '.join(cmd), cwd))
@@ skipping 460 matching lines @@
     return options, args
 
 
 def main(argv):
   dispatcher = subcommand.CommandDispatcher(__name__)
   return dispatcher.execute(OptionParser(), argv)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))