bpo-45012 Release GIL around stat in os.scandir

[skonieczny]

Releasing GIL allows other threads to continue
its work when os.scandir is fetching DirEntry.stat
info from file system.

It might be important in case of
slow or unresponsive file system.

https://bugs.python.org/issue45012

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[skonieczny]

@erlend-aasland I have squashed your suggestion into first commit

[erlend-aasland]

One more thing: please use reST markup in NEWS entries.

Suggested change

	DirEntry object returned by os.scandir release GIL around stat, lstat and fstatat syscalls.
	In :mod:`posix`, release GIL during ``stat()``, ``lstat()``, and
	``fstatat()`` syscalls. Patch by Stanisław Skonieczny.

See the devguide for a reST primer :)

[erlend-aasland]

I have squashed your suggestion into first commit

Thanks! I left a small remark about your NEWS entry as well.

[skonieczny]

Thanks! I will squash it into first commit, but I would like to keep info about os.scandir in the NEWS to make clear that this commit does not fix other function from os module.

[skonieczny]

@erlend-aasland
I have applied your changes and squashed everything into one commit.

[erlend-aasland]

Thanks! I will squash it into first commit, but I would like to keep info about os.scandir in the NEWS to make clear that this commit does not fix other function from os module.

Ok. In that case, I'd consider rewording the NEWS entry further. Perhaps something like this:

In :func:`os.DirEntry.stat`, release GIL during ``stat()``, ``lstat()``, and
``fstatat()`` syscalls . Patch by Stanisław Skonieczny.

[erlend-aasland]

By the way, using git fetch --no-ff main instead of git rebase main makes the PR easier to review, as it works well with GitHub. Also, we squash every PR that's merged into main, so it does not matter it you've got a lot of amending commits.

[skonieczny]

Also, we squash every PR that's merged into main, so it does not matter it you've got a lot of amending commits.

Good to know. Thanks!

[ambv]

dir_fd isn't exposed to Python code and it's only set during object creation (in DirEntry_from_posix_info) so AFAICT this is safe.

[skonieczny]

@ambv Is there a chance to backport it to older python versions?

[ambv]

Not really. 3.10.0 is past rc2 and bugfix releases don't accept performance improvements.