gh-112175: Add `eval_breaker` to `PyThreadState` (#115194)

This change adds an `eval_breaker` field to `PyThreadState`. The primary
motivation is for performance in free-threaded builds: with thread-local eval
breakers, we can stop a specific thread (e.g., for an async exception) without
interrupting other threads.

The source of truth for the global instrumentation version is stored in the
`instrumentation_version` field in PyInterpreterState. Threads usually read the
version from their local `eval_breaker`, where it continues to be colocated
with the eval breaker bits.

1 files changed, 4 insertions, 7 deletions

diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 394a997..652e69b 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -276,11 +276,7 @@ trip_signal(int sig_num)
        cleared in PyErr_CheckSignals() before .tripped. */
     _Py_atomic_store_int(&is_tripped, 1);
 
-    /* Signals are always handled by the main interpreter */
-    PyInterpreterState *interp = _PyInterpreterState_Main();
-
-    /* Notify ceval.c */
-    _PyEval_SignalReceived(interp);
+    _PyEval_SignalReceived();
 
     /* And then write to the wakeup fd *after* setting all the globals and
        doing the _PyEval_SignalReceived. We used to write to the wakeup fd
@@ -303,6 +299,7 @@ trip_signal(int sig_num)
 
     int fd = wakeup.fd;
     if (fd != INVALID_FD) {
+        PyInterpreterState *interp = _PyInterpreterState_Main();
         unsigned char byte = (unsigned char)sig_num;
 #ifdef MS_WINDOWS
         if (wakeup.use_send) {
@@ -1770,8 +1767,8 @@ PyErr_CheckSignals(void)
        Python code to ensure signals are handled. Checking for the GC here
        allows long running native code to clean cycles created using the C-API
        even if it doesn't run the evaluation loop */
-    if (_Py_eval_breaker_bit_is_set(tstate->interp, _PY_GC_SCHEDULED_BIT)) {
-        _Py_set_eval_breaker_bit(tstate->interp, _PY_GC_SCHEDULED_BIT, 0);
+    if (_Py_eval_breaker_bit_is_set(tstate, _PY_GC_SCHEDULED_BIT)) {
+        _Py_unset_eval_breaker_bit(tstate, _PY_GC_SCHEDULED_BIT);
         _Py_RunGC(tstate);
     }