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gh-116322: Add Py_mod_gil module slot (#116882)

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This PR adds the ability to enable the GIL if it was disabled at
interpreter startup, and modifies the multi-phase module initialization
path to enable the GIL when loading a module, unless that module's spec
includes a slot indicating it can run safely without the GIL.

PEP 703 called the constant for the slot `Py_mod_gil_not_used`; I went
with `Py_MOD_GIL_NOT_USED` for consistency with gh-104148.

A warning will be issued up to once per interpreter for the first
GIL-using module that is loaded. If `-v` is given, a shorter message
will be printed to stderr every time a GIL-using module is loaded
(including the first one that issues a warning).
This commit is contained in:
Brett Simmers 2024-05-03 08:30:55 -07:00 • committed by GitHub
parent 3e818afb9b
commit c2627d6eea
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123 changed files with 376 additions and 62 deletions
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38
Doc/c-api/module.rst
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@ -411,6 +411,31 @@ The available slot types are:
.. versionadded:: 3.12
.. c:macro:: Py_mod_gil
Specifies one of the following values:
.. c:macro:: Py_MOD_GIL_USED
The module depends on the presence of the global interpreter lock (GIL),
and may access global state without synchronization.
.. c:macro:: Py_MOD_GIL_NOT_USED
The module is safe to run without an active GIL.
This slot is ignored by Python builds not configured with
:option:`--disable-gil`. Otherwise, it determines whether or not importing
this module will cause the GIL to be automatically enabled. See
:envvar:`PYTHON_GIL` and :option:`-X gil <-X>` for more detail.
Multiple ``Py_mod_gil`` slots may not be specified in one module definition.
If ``Py_mod_gil`` is not specified, the import machinery defaults to
``Py_MOD_GIL_USED``.
.. versionadded: 3.13
See :PEP:`489` for more details on multi-phase initialization.
Low-level module creation functions
@ -609,6 +634,19 @@ state:
.. versionadded:: 3.9
.. c:function:: int PyModule_ExperimentalSetGIL(PyObject *module, void *gil)
Indicate that *module* does or does not support running without the global
interpreter lock (GIL), using one of the values from
:c:macro:`Py_mod_gil`. It must be called during *module*'s initialization
function. If this function is not called during module initialization, the
import machinery assumes the module does not support running without the
GIL. This function is only available in Python builds configured with
:option:`--disable-gil`.
Return ``-1`` on error, ``0`` on success.
.. versionadded:: 3.13
Module lookup
^^^^^^^^^^^^^