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gh-44098: Release the GIL while calling mmap() in the mmap module on Windows #14114

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gh-44098: Release the GIL while calling mmap() in the mmap module on Windows #14114

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bpo-1572968: Release the GIL while calling mmap() in the mmap module
ZackerySpytz Jun 15, 2019
45399a6
Merge branch 'main' into bpo-1572968-GIL-mmap-module
nanjekyejoannah Oct 7, 2022
c196466
Merge remote-tracking branch 'upstream/main' into bpo-1572968-GIL-mma…
ZackerySpytz Dec 12, 2022
9e1d7bd
Merge branch 'main' into bpo-1572968-GIL-mmap-module
erlend-aasland Jan 5, 2024
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2019-06-15-09-37-33.bpo-1572968.zftonM.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Release the GIL in :class:`mmap.mmap`.
2 changes: 2 additions & 0 deletions Modules/mmapmodule.c
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Expand Up @@ -1562,12 +1562,14 @@ new_mmap_object(PyTypeObject *type, PyObject *args, PyObject *kwdict)
off_lo = (DWORD)(offset & 0xFFFFFFFF);
/* For files, it would be sufficient to pass 0 as size.
For anonymous maps, we have to pass the size explicitly. */
Py_BEGIN_ALLOW_THREADS
m_obj->map_handle = CreateFileMappingA(m_obj->file_handle,
NULL,
flProtect,
size_hi,
size_lo,
m_obj->tagname);
Py_END_ALLOW_THREADS
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This should be after the MapViewOfFile call. We can probably restructure the function to store results in locals and then determine success/failure after we have the GIL back

if (m_obj->map_handle != NULL) {
m_obj->data = (char *) MapViewOfFile(m_obj->map_handle,
dwDesiredAccess,
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