commit d2a8e5b42c5e9c4e745a0589043a8aebb49f8ca2
author Victor Stinner <vstinner@python.org> Fri Mar 20 13:38:58 2020 +0100
committer GitHub <noreply@github.com> Fri Mar 20 13:38:58 2020 +0100
tree bf76400eb6529986ba4319faf4664a70a7303869
parent da2914db4b6f786a1e9f0b424efeeb6ca9418912

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.

Modules/signalmodule.c

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 @@
 #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 @@
     }
 #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 @@
         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 @@
 int
 PyErr_CheckSignals(void)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    if (!is_main(runtime)) {
+    if (!thread_can_handle_signals()) {
         return 0;
     }
 
@@ -1769,8 +1766,7 @@
 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 @@
 int
 _PyOS_IsMainThread(void)
 {
-    _PyRuntimeState *runtime = &_PyRuntime;
-    return is_main(runtime);
+    return thread_can_handle_signals();
 }
 
 #ifdef MS_WINDOWS