diff options
| -rw-r--r-- | lib/spack/llnl/util/lock.py | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/lib/spack/llnl/util/lock.py b/lib/spack/llnl/util/lock.py index 86ad9d60e1..2e44a94798 100644 --- a/lib/spack/llnl/util/lock.py +++ b/lib/spack/llnl/util/lock.py @@ -91,21 +91,25 @@ class Lock(object): start_time = time.time() while (time.time() - start_time) < timeout: try: - # If this is already open read-only and we want to - # upgrade to an exclusive write lock, close first. - if self._file is not None: - if op == fcntl.LOCK_EX and self._file.mode == 'r': - self._file.close() - self._file = None - - # Open reader locks read-only if possible. - # lock doesn't exist, open RW + create if it doesn't exist. + # If we could write the file, we'd have opened it 'r+'. + # Raise an error when we attempt to upgrade to a write lock. + if op == fcntl.LOCK_EX: + if self._file and self._file.mode == 'r': + raise LockError( + "Can't take exclusive lock on read-only file: %s" + % self.path) + + # Create file and parent directories if they don't exist. if self._file is None: self._ensure_parent_directory() - os_mode, fd_mode = os.O_RDONLY, 'r' - if op == fcntl.LOCK_EX or not os.path.exists(self.path): - os_mode, fd_mode = (os.O_RDWR | os.O_CREAT), 'r+' + # Prefer to open 'r+' to allow upgrading to write + # lock later if possible. Open read-only if we can't + # write the lock file at all. + os_mode, fd_mode = (os.O_RDWR | os.O_CREAT), 'r+' + if os.path.exists(self.path) and not os.access( + self.path, os.W_OK): + os_mode, fd_mode = os.O_RDONLY, 'r' fd = os.open(self.path, os_mode) self._file = os.fdopen(fd, fd_mode) |