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# Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
# Spack Project Developers. See the top-level COPYRIGHT file for details.
#
# SPDX-License-Identifier: (Apache-2.0 OR MIT)
"""Wrapper for ``llnl.util.lock`` allows locking to be enabled/disabled."""
import os
import stat
import sys
from typing import Optional, Tuple
import llnl.util.lock
# import some llnl.util.lock names as though they're part of spack.util.lock
from llnl.util.lock import LockError # noqa: F401
from llnl.util.lock import LockTimeoutError # noqa: F401
from llnl.util.lock import LockUpgradeError # noqa: F401
from llnl.util.lock import ReadTransaction # noqa: F401
from llnl.util.lock import WriteTransaction # noqa: F401
import spack.error
import spack.paths
class Lock(llnl.util.lock.Lock):
"""Lock that can be disabled.
This overrides the ``_lock()`` and ``_unlock()`` methods from
``llnl.util.lock`` so that all the lock API calls will succeed, but
the actual locking mechanism can be disabled via ``_enable_locks``.
"""
def __init__(
self,
path: str,
*,
start: int = 0,
length: int = 0,
default_timeout: Optional[float] = None,
debug: bool = False,
desc: str = "",
enable: Optional[bool] = None,
) -> None:
enable_lock = enable
if sys.platform == "win32":
enable_lock = False
elif sys.platform != "win32" and enable_lock is None:
enable_lock = True
self._enable = enable_lock
super().__init__(
path,
start=start,
length=length,
default_timeout=default_timeout,
debug=debug,
desc=desc,
)
def _lock(self, op: int, timeout: Optional[float] = 0.0) -> Tuple[float, int]:
if self._enable:
return super()._lock(op, timeout)
return 0.0, 0
def _unlock(self) -> None:
"""Unlock call that always succeeds."""
if self._enable:
super()._unlock()
def cleanup(self, *args) -> None:
if self._enable:
super().cleanup(*args)
def check_lock_safety(path: str) -> None:
"""Do some extra checks to ensure disabling locks is safe.
This will raise an error if ``path`` can is group- or world-writable
AND the current user can write to the directory (i.e., if this user
AND others could write to the path).
This is intended to run on the Spack prefix, but can be run on any
path for testing.
"""
if os.access(path, os.W_OK):
stat_result = os.stat(path)
uid, gid = stat_result.st_uid, stat_result.st_gid
mode = stat_result[stat.ST_MODE]
writable = None
if (mode & stat.S_IWGRP) and (uid != gid):
# spack is group-writeable and the group is not the owner
writable = "group"
elif mode & stat.S_IWOTH:
# spack is world-writeable
writable = "world"
if writable:
msg = f"Refusing to disable locks: spack is {writable}-writable."
long_msg = (
f"Running a shared spack without locks is unsafe. You must "
f"restrict permissions on {path} or enable locks."
)
raise spack.error.SpackError(msg, long_msg)
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