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.

1 files changed, 12 insertions, 17 deletions

diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index a26ae7d..fa3b01d 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -190,12 +190,10 @@ itimer_retval(struct itimerval *iv)
 #endif
 
 static int
-is_main(_PyRuntimeState *runtime)
+thread_can_handle_signals(void)
 {
-    unsigned long thread = PyThread_get_thread_ident();
-    PyInterpreterState *interp = _PyRuntimeState_GetThreadState(runtime)->interp;
-    return (thread == runtime->main_thread
-            && interp == runtime->interpreters.main);
+    PyThreadState *tstate = _PyThreadState_GET();
+    return _Py_ThreadCanHandleSignals(tstate);
 }
 
 static PyObject *
@@ -482,10 +480,10 @@ signal_signal_impl(PyObject *module, int signalnum, PyObject *handler)
     }
 #endif
 
-    _PyRuntimeState *runtime = &_PyRuntime;
-    if (!is_main(runtime)) {
+    if (!thread_can_handle_signals()) {
         PyErr_SetString(PyExc_ValueError,
-                        "signal only works in main thread");
+                        "signal only works in main thread "
+                        "of the main interpreter");
         return NULL;
     }
     if (signalnum < 1 || signalnum >= NSIG) {
@@ -700,10 +698,10 @@ signal_set_wakeup_fd(PyObject *self, PyObject *args, PyObject *kwds)
         return NULL;
 #endif
 
-    _PyRuntimeState *runtime = &_PyRuntime;
-    if (!is_main(runtime)) {
+    if (!thread_can_handle_signals()) {
         PyErr_SetString(PyExc_ValueError,
-                        "set_wakeup_fd only works in main thread");
+                        "set_wakeup_fd only works in main thread "
+                        "of the main interpreter");
         return NULL;
     }
 
@@ -1675,8 +1673,7 @@ finisignal(void)
 int
 PyErr_CheckSignals(void)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    if (!is_main(runtime)) {
+    if (!thread_can_handle_signals()) {
         return 0;
     }
 
@@ -1769,8 +1766,7 @@ int
 PyOS_InterruptOccurred(void)
 {
     if (_Py_atomic_load_relaxed(&Handlers[SIGINT].tripped)) {
-        _PyRuntimeState *runtime = &_PyRuntime;
-        if (!is_main(runtime)) {
+        if (!thread_can_handle_signals()) {
             return 0;
         }
         _Py_atomic_store_relaxed(&Handlers[SIGINT].tripped, 0);
@@ -1803,8 +1799,7 @@ _PySignal_AfterFork(void)
 int
 _PyOS_IsMainThread(void)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    return is_main(runtime);
+    return thread_can_handle_signals();
 }
 
 #ifdef MS_WINDOWS