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Allow C extensions to declare compatibility with free-threading #116322

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Tracked by #108219
swtaarrs opened this issue Mar 4, 2024 · 3 comments
Closed
Tracked by #108219

Allow C extensions to declare compatibility with free-threading #116322

swtaarrs opened this issue Mar 4, 2024 · 3 comments
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interpreter-core (Objects, Python, Grammar, and Parser dirs) topic-free-threading type-feature A feature request or enhancement

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@swtaarrs
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swtaarrs commented Mar 4, 2024

Feature or enhancement

There are a few pieces to this:

  1. Add a Py_mod_gil slot, as described in PEP 703, that multi-phase init modules can use to indicate that they support free-threading.
  2. Add a PyModule_ExperimentalSetGIL() function (discussed here) that single-phase init modules can use in place of Py_mod_gil.
  3. Mark all built-in modules as free-threading compatible with one of the above mechanisms.
  4. Enable the GIL while loading a C module and leave it permanently enabled if the module does not declare free-threading compatibility.

1-3 are addressed in gh-116882; 4 will be addressed in a separate PR.

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@swtaarrs
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What warning category should this issue? ImportWarning sounds like a good fit at first, but it's ignored by the default warning filters, which we don't want. Of the categories not ignored by default, RuntimeWarning seems like the best fit to me.

@swtaarrs swtaarrs changed the title Implement Py_mod_gil slot for free-threading-safe extensions Allow C extensions to declare compatibility with free-threading May 2, 2024
colesbury pushed a commit that referenced this issue May 3, 2024
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).
encukou added a commit to encukou/cpython that referenced this issue May 6, 2024
colesbury pushed a commit that referenced this issue May 7, 2024
Add the ability to enable/disable the GIL at runtime, and use that in
the C module loading code.

We can't know before running a module init function if it supports
free-threading, so the GIL is temporarily enabled before doing so. If
the module declares support for running without the GIL, the GIL is
later disabled. Otherwise, the GIL is permanently enabled, and will
never be disabled again for the life of the current interpreter.
@colesbury
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@swtaarrs is this finished now?

@swtaarrs
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swtaarrs commented May 7, 2024

Yep!

@swtaarrs swtaarrs closed this as completed May 7, 2024
SonicField pushed a commit to SonicField/cpython that referenced this issue May 8, 2024
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 pythongh-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).
SonicField pushed a commit to SonicField/cpython that referenced this issue May 8, 2024
SonicField pushed a commit to SonicField/cpython that referenced this issue May 8, 2024
…thon#118560)

Add the ability to enable/disable the GIL at runtime, and use that in
the C module loading code.

We can't know before running a module init function if it supports
free-threading, so the GIL is temporarily enabled before doing so. If
the module declares support for running without the GIL, the GIL is
later disabled. Otherwise, the GIL is permanently enabled, and will
never be disabled again for the life of the current interpreter.
colesbury added a commit to colesbury/cpython that referenced this issue Jul 25, 2024
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Jul 25, 2024
(cherry picked from commit 9bb2e46)

Co-authored-by: Serhiy Storchaka <[email protected]>
AlexWaygood added a commit to colesbury/cpython that referenced this issue Jul 25, 2024
kumaraditya303 pushed a commit that referenced this issue Jul 25, 2024
gh-116322: Fix typo in the GH-ifdef check (GH-122268)
(cherry picked from commit 9bb2e46)

Co-authored-by: Serhiy Storchaka <[email protected]>
stefanholek added a commit to stefanholek/rl that referenced this issue Oct 14, 2024
This means: "Do not re-enable the GIL when importing rl.readline."

See python/cpython#116322
See python/cpython#116882
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Labels
interpreter-core (Objects, Python, Grammar, and Parser dirs) topic-free-threading type-feature A feature request or enhancement
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