bpo-40010: COMPUTE_EVAL_BREAKER() checks for subinterpreter (GH-19087)

COMPUTE_EVAL_BREAKER() now also checks if the Python thread state
belongs to the main interpreter. Don't break the evaluation loop if
there are pending signals but the Python thread state it belongs to a
subinterpeter.

* Add _Py_IsMainThread() function.
* Add _Py_ThreadCanHandleSignals() function.

2 files changed, 3 insertions, 30 deletions

diff --git a/Python/ceval.c b/Python/ceval.c
index 30599a5..86aa225 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -136,14 +136,6 @@ is_tstate_valid(PyThreadState *tstate)
 #endif
 
 
-/* Only handle signals on the main thread of the main interpreter. */
-static int
-thread_can_handle_signals(void)
-{
-    return (PyThread_get_thread_ident() == _PyRuntime.main_thread);
-}
-
-
 /* This can set eval_breaker to 0 even though gil_drop_request became
    1.  We believe this is all right because the eval loop will release
    the GIL eventually anyway. */
@@ -156,7 +148,7 @@ COMPUTE_EVAL_BREAKER(PyThreadState *tstate,
     _Py_atomic_store_relaxed(&ceval2->eval_breaker,
         _Py_atomic_load_relaxed(&ceval->gil_drop_request)
         | (_Py_atomic_load_relaxed(&ceval->signals_pending)
-           && thread_can_handle_signals())
+           && _Py_ThreadCanHandleSignals(tstate))
         | _Py_atomic_load_relaxed(&ceval2->pending.calls_to_do)
         | ceval2->pending.async_exc);
 }
@@ -598,17 +590,7 @@ Py_AddPendingCall(int (*func)(void *), void *arg)
 static int
 handle_signals(PyThreadState *tstate)
 {
-    _PyRuntimeState *runtime = tstate->interp->runtime;
-
-    if (!thread_can_handle_signals()) {
-        return 0;
-    }
-    /*
-     * Ensure that the thread isn't currently running some other
-     * interpreter.
-     */
-    PyInterpreterState *interp = tstate->interp;
-    if (interp != runtime->interpreters.main) {
+    if (!_Py_ThreadCanHandleSignals(tstate)) {
         return 0;
     }
 
@@ -624,11 +606,8 @@ handle_signals(PyThreadState *tstate)
 static int
 make_pending_calls(PyThreadState *tstate)
 {
-
-    _PyRuntimeState *runtime = tstate->interp->runtime;
-
     /* only service pending calls on main thread */
-    if (PyThread_get_thread_ident() != runtime->main_thread) {
+    if (!_Py_IsMainThread()) {
         return 0;
     }
 
diff --git a/Python/pystate.c b/Python/pystate.c
index a792cc5..621318f 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -169,12 +169,6 @@ _PyRuntimeState_ReInitThreads(_PyRuntimeState *runtime)
 #define HEAD_UNLOCK(runtime) \
     PyThread_release_lock((runtime)->interpreters.mutex)
 
-int
-_Py_IsMainInterpreter(PyThreadState* tstate)
-{
-    return (tstate->interp == tstate->interp->runtime->interpreters.main);
-}
-
 /* Forward declaration */
 static void _PyGILState_NoteThreadState(
     struct _gilstate_runtime_state *gilstate, PyThreadState* tstate);