Synnefo » snf-ganeti

    try:

      # Support passing in a single resource to acquire rather than many

      if isinstance(names, basestring):

        names = [names]

      else:

        names.sort()

      acquire_list = []

      # First we look the locks up on __lockdict. We have no way of being sure

      # they will still be there after, but this makes it a lot faster should

      # just one of them be the already wrong

      for lname in names:

          lock = self.__lockdict[lname] # raises KeyError if the lock is not there

          acquire_list.append((lname, lock))

        except (KeyError):

          raise errors.LockError('non-existing lock in set (%s)' % lname)

      # This will hold the locknames we effectively acquired.

      acquired = set()

      # Now acquire_list contains a sorted list of resources and locks we want.

      # In order to get them we loop on this (private) list and acquire() them.

      # We gave no real guarantee they will still exist till this is done but

      # .acquire() itself is safe and will alert us if the lock gets deleted.

      for (lname, lock) in acquire_list:

        try:

          lock.acquire(shared=shared) # raises LockError if the lock is deleted

          try:

            # now the lock cannot be deleted, we have it!

            self._add_owned(lname)

            acquired.add(lname)

          except:

            # We shouldn't have problems adding the lock to the owners list, but

            # if we did we'll try to release this lock and re-raise exception.

            # Of course something is going to be really wrong, after this.

            lock.release()

            raise

        except (errors.LockError):

          name_fail = lname

          for lname in self._list_owned():

            self.__lockdict[lname].release()

            self._del_owned(lname)

          raise errors.LockError('non-existing lock in set (%s)' % name_fail)

    except:

      raise