gh-111964: Implement stop-the-world pauses (gh-112471)

The `--disable-gil` builds occasionally need to pause all but one thread.  Some
examples include:

* Cyclic garbage collection, where this is often called a "stop the world event"
* Before calling `fork()`, to ensure a consistent state for internal data structures
* During interpreter shutdown, to ensure that daemon threads aren't accessing Python objects

This adds the following functions to implement global and per-interpreter pauses:

* `_PyEval_StopTheWorldAll()` and `_PyEval_StartTheWorldAll()` (for the global runtime)
* `_PyEval_StopTheWorld()` and `_PyEval_StartTheWorld()` (per-interpreter)

(The function names may change.)

These functions are no-ops outside of the `--disable-gil` build.

1 files changed, 1 insertions, 1 deletions

diff --git a/Include/cpython/pystate.h b/Include/cpython/pystate.h
index 1091394..60b056b 100644
--- a/Include/cpython/pystate.h
+++ b/Include/cpython/pystate.h
@@ -102,7 +102,7 @@ struct _ts {
 #endif
     int _whence;
 
-    /* Thread state (_Py_THREAD_ATTACHED, _Py_THREAD_DETACHED, _Py_THREAD_GC).
+    /* Thread state (_Py_THREAD_ATTACHED, _Py_THREAD_DETACHED, _Py_THREAD_SUSPENDED).
        See Include/internal/pycore_pystate.h for more details. */
     int state;