gh-119132: Remove "experimental" tag from the CPython free-threading. (gh-135550)

* gh-119132: Remove "experimental" tag from the CPython free-threading build

* Address code review

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

* Add NEWS.d

* Regen configure.ac

* Update doc

* Update

* Update

* Update

* Update Doc/howto/free-threading-python.rst

Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

* Update ctypes.rst

* Update

* Update Doc/howto/free-threading-python.rst

Co-authored-by: T. Wouters <thomas@python.org>

* Apply suggestions from code review

Co-authored-by: T. Wouters <thomas@python.org>
Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

---------

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>
Co-authored-by: T. Wouters <thomas@python.org>

Doc/howto/free-threading-extensions.rst

@@ -6,8 +6,8 @@
 C API Extension Support for Free Threading
 ******************************************
 
-Starting with the 3.13 release, CPython has experimental support for running
+Starting with the 3.13 release, CPython has support for running with
-with the :term:`global interpreter lock` (GIL) disabled in a configuration
+the :term:`global interpreter lock` (GIL) disabled in a configuration
 called :term:`free threading`.  This document describes how to adapt C API
 extensions to support free threading.
 

Doc/howto/free-threading-python.rst

@@ -1,18 +1,21 @@
 .. _freethreading-python-howto:
 
-**********************************************
+*********************************
-Python experimental support for free threading
+Python support for free threading
-**********************************************
+*********************************
 
-Starting with the 3.13 release, CPython has experimental support for a build of
+Starting with the 3.13 release, CPython has support for a build of
 Python called :term:`free threading` where the :term:`global interpreter lock`
 (GIL) is disabled.  Free-threaded execution allows for full utilization of the
 available processing power by running threads in parallel on available CPU cores.
 While not all software will benefit from this automatically, programs
 designed with threading in mind will run faster on multi-core hardware.
 
-**The free-threaded mode is experimental** and work is ongoing to improve it:
+The free-threaded mode is working and continues to be improved, but
-expect some bugs and a substantial single-threaded performance hit.
+there is some additional overhead in single-threaded workloads compared
+to the regular build. Additionally, third-party packages, in particular ones
+with an :term:`extension module`, may not be ready for use in a
+free-threaded build, and will re-enable the :term:`GIL`.
 
 This document describes the implications of free threading
 for Python code.  See :ref:`freethreading-extensions-howto` for information on
@@ -43,7 +46,7 @@ Identifying free-threaded Python
 ================================
 
 To check if the current interpreter supports free-threading, :option:`python -VV <-V>`
-and :data:`sys.version` contain "experimental free-threading build".
+and :data:`sys.version` contain "free-threading build".
 The new :func:`sys._is_gil_enabled` function can be used to check whether
 the GIL is actually disabled in the running process.
 

Doc/library/ctypes.rst

@@ -882,7 +882,7 @@ invalid non-\ ``NULL`` pointers would crash Python)::
 Thread safety without the GIL
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-In Python 3.13, the :term:`GIL` may be disabled on :term:`experimental free threaded <free threading>` builds.
+From Python 3.13 onward, the :term:`GIL` can be disabled on :term:`free threaded <free threading>` builds.
 In ctypes, reads and writes to a single object concurrently is safe, but not across multiple objects:
 
    .. code-block:: pycon

Doc/library/threading.rst

@@ -102,7 +102,7 @@ CPU-bound tasks, as only one thread can execute Python bytecode at a time.
 Despite this, threads remain a useful tool for achieving concurrency in many
 scenarios.
 
-As of Python 3.13, experimental :term:`free-threaded <free threading>` builds
+As of Python 3.13, :term:`free-threaded <free threading>` builds
 can disable the GIL, enabling true parallel execution of threads, but this
 feature is not available by default (see :pep:`703`).
 

Doc/using/configure.rst

@@ -290,8 +290,8 @@ General Options
 
 .. option:: --disable-gil
 
-   Enables **experimental** support for running Python without the
+   Enables support for running Python without the :term:`global interpreter
-   :term:`global interpreter lock` (GIL): free threading build.
+   lock` (GIL): free threading build.
 
    Defines the ``Py_GIL_DISABLED`` macro and adds ``"t"`` to
    :data:`sys.abiflags`.

Lib/platform.py

@@ -1144,7 +1144,7 @@ def _sys_version(sys_version=None):
         # CPython
         cpython_sys_version_parser = re.compile(
             r'([\w.+]+)\s*'  # "version<space>"
-            r'(?:experimental free-threading build\s+)?' # "free-threading-build<space>"
+            r'(?:free-threading build\s+)?' # "free-threading-build<space>"
             r'\(#?([^,]+)'  # "(#buildno"
             r'(?:,\s*([\w ]*)'  # ", builddate"
             r'(?:,\s*([\w :]*))?)?\)\s*'  # ", buildtime)<space>"

Misc/NEWS.d/next/Build/2025-06-16-07-20-28.gh-issue-119132.fcI8s7.rst

@@ -0,0 +1 @@
+Remove "experimental" tag from the CPython free-threading build.

PCbuild/build.bat

@@ -33,7 +33,7 @@ echo.  -k  Attempt to kill any running Pythons before building (usually done
 echo.      automatically by the pythoncore project)
 echo.  --pgo          Build with Profile-Guided Optimization.  This flag
 echo.                 overrides -c and -d
-echo.  --disable-gil  Enable experimental support for running without the GIL.
+echo.  --disable-gil  Enable support for running without the GIL.
 echo.  --test-marker  Enable the test marker within the build.
 echo.  --regen        Regenerate all opcodes, grammar and tokens.
 echo.  --experimental-jit          Enable the experimental just-in-time compiler.

Python/getversion.c

@@ -15,7 +15,7 @@ void _Py_InitVersion(void)
     }
     initialized = 1;
 #ifdef Py_GIL_DISABLED
-    const char *buildinfo_format = "%.80s experimental free-threading build (%.80s) %.80s";
+    const char *buildinfo_format = "%.80s free-threading build (%.80s) %.80s";
 #else
     const char *buildinfo_format = "%.80s (%.80s) %.80s";
 #endif

configure

@@ -1826,8 +1826,8 @@ Optional Features:
                           no)
   --enable-profiling      enable C-level code profiling with gprof (default is
                           no)
-  --disable-gil           enable experimental support for running without the
+  --disable-gil           enable support for running without the GIL (default
-                          GIL (default is no)
+                          is no)
   --enable-pystats        enable internal statistics gathering (default is no)
   --enable-optimizations  enable expensive, stable optimizations (PGO, etc.)
                           (default is no)

configure.ac

@@ -1716,7 +1716,7 @@ ABI_THREAD=""
 # --disable-gil
 AC_MSG_CHECKING([for --disable-gil])
 AC_ARG_ENABLE([gil],
-  [AS_HELP_STRING([--disable-gil], [enable experimental support for running without the GIL (default is no)])],
+  [AS_HELP_STRING([--disable-gil], [enable support for running without the GIL (default is no)])],
   [AS_VAR_IF([enable_gil], [yes], [disable_gil=no], [disable_gil=yes])], [disable_gil=no]
 )
 AC_MSG_RESULT([$disable_gil])