Fix infinite recursion in PrebuiltsReady when graph is cyclic.

parallel_emerge

 #!/usr/bin/python2.6
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Program to run emerge in parallel, for significant speedup.
 
 Usage:
  ./parallel_emerge [--board=BOARD] [--workon=PKGS] [--no-workon-deps]
                    [emerge args] package"
@@ skipping 801 matching lines @@
           cache: A dict, where the results are stored.
 
         Returns:
           True iff the prebuilts are ready for pkg and all deps.
         """
         if pkg in cache:
           return cache[pkg]
         if pkg not in pkg_db:
           cache[pkg] = False
         else:
+          cache[pkg] = True
           for dep in deps_map[pkg]["needs"]:
             if not PrebuiltsReady(dep, pkg_db, cache):
               cache[pkg] = False
               break
-        return cache.setdefault(pkg, True)
+        return cache[pkg]
 
       def LastModifiedWithDeps(pkg, pkg_db, cache):
         """Calculate the last modified time of a package and its dependencies.
 
         This function looks at all the packages needed by the specified package
         and checks the most recent modification time of all of those packages.
         If the dependencies of a package were modified more recently than the
         package itself, then we know the package needs to be rebuilt.
 
         Args:
@@ skipping 420 matching lines @@
       for db_pkg in final_db.match_pkgs(pkg):
         print "Adding %s to world" % db_pkg.cp
         new_world_pkgs.append(db_pkg.cp)
     if new_world_pkgs:
       world_set.update(new_world_pkgs)
 
   print "Done"
 
 if __name__ == "__main__":
   main()