Initial step into making Dependency thread safe

R=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/7892034

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@101135 0039d316-1c4b-4281-b951-d872f2087c98

gclient.py

@@ -145,9 +145,8 @@ class Dependency(GClientKeywords, gclient_utils.WorkItem):
     # self.dependencies and self.requirements are read and modified from
     # multiple threads at the same time. Sad.
     GClientKeywords.__init__(self)
-    gclient_utils.WorkItem.__init__(self)
+    gclient_utils.WorkItem.__init__(self, name)
     self.parent = parent
-    self.name = name
     self.url = url
     self.parsed_url = None
     # These 2 are only set in .gclient and not in DEPS files.
@@ -169,8 +168,6 @@ class Dependency(GClientKeywords, gclient_utils.WorkItem):
     self.processed = False
     # This dependency had its hook run
     self.hooks_ran = False
-    # Required dependencies to run before running this one:
-    self.requirements = set()
 
     # Post process the url to remove trailing slashes.
     if isinstance(self.url, basestring):
@@ -201,7 +198,7 @@ class Dependency(GClientKeywords, gclient_utils.WorkItem):
     # self.parent is implicitly a requirement. This will be recursive by
     # definition.
     if self.parent and self.parent.name:
-      self.requirements.add(self.parent.name)
+      self._requirements.add(self.parent.name)
 
     # For a tree with at least 2 levels*, the leaf node needs to depend
     # on the level higher up in an orderly way.
@@ -219,10 +216,10 @@ class Dependency(GClientKeywords, gclient_utils.WorkItem):
       for i in range(0, root_deps.index(self.parent)):
         value = root_deps[i]
         if value.name:
-          self.requirements.add(value.name)
+          self._requirements.add(value.name)
 
     if isinstance(self.url, self.FromImpl):
-      self.requirements.add(self.url.module_name)
+      self._requirements.add(self.url.module_name)
 
     if self.name and self.should_process:
       def yield_full_tree(root):
@@ -238,7 +235,7 @@ class Dependency(GClientKeywords, gclient_utils.WorkItem):
           continue
         # Step 1: Find any requirements self may need.
         if self.name.startswith(posixpath.join(obj.name, '')):
-          self.requirements.add(obj.name)
+          self._requirements.add(obj.name)
         # Step 2: Find any requirements self may impose.
         if obj.name.startswith(posixpath.join(self.name, '')):
           obj.requirements.add(self.name)

gclient_utils.py

@@ -456,19 +456,45 @@ def GetGClientRootAndEntries(path=None):
   return config_dir, env['entries']
 
 
+def lockedmethod(method):
+  """Method decorator that holds self.lock for the duration of the call."""
+  def inner(self, *args, **kwargs):
+    try:
+      try:
+        self.lock.acquire()
+      except KeyboardInterrupt:
+        print >> sys.stderr, 'Was deadlocked'
+        raise
+      return method(self, *args, **kwargs)
+    finally:
+      self.lock.release()
+  return inner
+
+
 class WorkItem(object):
   """One work item."""
-  def __init__(self):
+  def __init__(self, name):
     # A list of string, each being a WorkItem name.
-    self.requirements = []
+    self._requirements = set()
     # A unique string representing this work item.
-    self.name = None
+    self._name = name
+    self.lock = threading.RLock()
 
+  @lockedmethod
   def run(self, work_queue):
     """work_queue is passed as keyword argument so it should be
     the last parameters of the function when you override it."""
     pass
 
+  @property
+  def name(self):
+    return self._name
+
+  @property
+  @lockedmethod
+  def requirements(self):
+    return tuple(self._requirements)
+
 
 class ExecutionQueue(object):
   """Runs a set of WorkItem that have interdependencies and were WorkItem are