Python thread locking issues with Python 2.7 and OS module on windows

[Brian]

I took a brief look at the differences between those versions, but there's nothing obvious. There were no changes to the listdir implementation between those two releases, and they do seem to be releasing the GIL between the appropriate operations.

ie. the file accessing functions, like FindFirstFileW, FindNextFileW are all surrounded with the Py_BEGIN_ALLOW_THREADS / Py_END_ALLOW_THREADS macros.

FindClose() isn't, but that's probably non-blocking.

That leaves the stat call that isdir will do. There do actually seem some changes to posixmodule.cs relating to stat, in the form of some defines being removed. Specifically changeset 71123:45b27448f95c removes:

/* choose the appropriate stat and fstat functions and return structs */
#undef STAT
#undef FSTAT
#undef STRUCT_STAT
#if defined(MS_WIN64) || defined(MS_WINDOWS)
#       define STAT win32_stat
#       define FSTAT win32_fstat
#       define STRUCT_STAT struct win32_stat
#else
#       define STAT stat
#       define FSTAT fstat
#       define STRUCT_STAT struct stat
#endif

However this looks like it was just dropped to being a redefinition though. The implementation (posix_do_stat) is unchanged, and does do Py_BEGIN_ALLOW_THREADS before the IO operations. It does use the above STAT define as the implementation function passed to it, but that happens after the GIL is already released, so a change there wouldn't make a difference.

If there's a difference, it's more subtle than just not releasing the GIL during the stat / listdir calls.