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XFAIL TestLocalPath.test_make_numbered_dir_multiprocess_safe (pytest-…
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…dev#11611)

The tested py.path.local.make_numbered_dir function is *not*
multiprocess safe, because is uses os.listdir which itself is not.

The os.listdir documentation explicitly states that:

> If a file is removed from or added to the directory during the call
> of this function, whether a name for that file be included is unspecified.

This can lead to a race when:

 1. process A attempts to create directory N
 2. the creation fails, as another process already created it in the meantime
 3. process A calls listdir to determine a more recent maxnum
 4. processes B+ repeatedly create newer directories and they delete directory N
 5. process A doesn't have directory N or any newer directory in listdir result
 6. process A attempts to create directory N again and raises

For details, see pytest-dev#11603 (comment)
and bellow.

Additionally, the test itself has a race in batch_make_numbered_dirs.
When this functions attempts to write to repro-N/foo,
repro-N may have already been removed by another process.

For details, see pytest-dev#11603 (comment)
and bellow.

---

The tested py.path.local.make_numbered_dir function is not used in pytest.
There is a different implementation in _pytest.pathlib.

Closes pytest-dev#11603
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hroncok authored Nov 14, 2023
1 parent 1eca302 commit 223e030
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3 changes: 3 additions & 0 deletions testing/_py/test_local.py
Original file line number Diff line number Diff line change
Expand Up @@ -868,6 +868,9 @@ def test_fspath_protocol_other_class(self, fake_fspath_obj):
py_path.strpath, str_path
)

@pytest.mark.xfail(
reason="#11603", raises=(error.EEXIST, error.ENOENT), strict=False
)
def test_make_numbered_dir_multiprocess_safe(self, tmpdir):
# https://github.com/pytest-dev/py/issues/30
with multiprocessing.Pool() as pool:
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