gh-104812: Run Pending Calls in any Thread (gh-104813)

For a while now, pending calls only run in the main thread (in the main interpreter). This PR changes things to allow any thread run a pending call, unless the pending call was explicitly added for the main thread to run.

Author: ericsnowcurrently

Include/cpython/ceval.h

@@ -22,6 +22,8 @@ PyAPI_FUNC(PyObject *) _PyEval_EvalFrameDefault(PyThreadState *tstate, struct _P
 PyAPI_FUNC(void) _PyEval_SetSwitchInterval(unsigned longmicroseconds);
 PyAPI_FUNC(unsigned long) _PyEval_GetSwitchInterval(void);
 
+PyAPI_FUNC(int) _PyEval_MakePendingCalls(PyThreadState*);
+
 PyAPI_FUNC(Py_ssize_t) PyUnstable_Eval_RequestCodeExtraIndex(freefunc);
 // Old name -- remove when this API changes:
 _Py_DEPRECATED_EXTERNALLY(3.12) staticinlinePy_ssize_t

Include/internal/pycore_ceval.h

@@ -27,7 +27,8 @@ PyAPI_FUNC(void) _PyEval_SignalReceived(PyInterpreterState *interp);
 PyAPI_FUNC(int) _PyEval_AddPendingCall(
 PyInterpreterState*interp,
 int (*func)(void*),
-void*arg);
+void*arg,
+intmainthreadonly);
 PyAPI_FUNC(void) _PyEval_SignalAsyncExc(PyInterpreterState*interp);
 #ifdefHAVE_FORK
 externPyStatus_PyEval_ReInitThreads(PyThreadState*tstate);

Include/internal/pycore_ceval_state.h

@@ -13,6 +13,24 @@ extern "C"{
 #include"pycore_gil.h"// struct _gil_runtime_state
 
 
+struct_pending_calls{
+intbusy;
+PyThread_type_locklock;
+/* Request for running pending calls. */
+_Py_atomic_intcalls_to_do;
+/* Request for looking at the `async_exc` field of the current
+ thread state.
+ Guarded by the GIL. */
+intasync_exc;
+#defineNPENDINGCALLS 32
+struct_pending_call{
+int (*func)(void*);
+void*arg;
+ } calls[NPENDINGCALLS];
+intfirst;
+intlast;
+};
+
 typedefenum{
 PERF_STATUS_FAILED=-1, // Perf trampoline is in an invalid state
 PERF_STATUS_NO_INIT=0, // Perf trampoline is not initialized
@@ -49,6 +67,8 @@ struct _ceval_runtime_state{
  the main thread of the main interpreter can handle signals: see
  _Py_ThreadCanHandleSignals(). */
 _Py_atomic_intsignals_pending;
+/* Pending calls to be made only on the main thread. */
+struct_pending_callspending_mainthread;
 };
 
 #ifdefPY_HAVE_PERF_TRAMPOLINE
@@ -62,24 +82,6 @@ struct _ceval_runtime_state{
 #endif
 
 
-struct_pending_calls{
-intbusy;
-PyThread_type_locklock;
-/* Request for running pending calls. */
-_Py_atomic_intcalls_to_do;
-/* Request for looking at the `async_exc` field of the current
- thread state.
- Guarded by the GIL. */
-intasync_exc;
-#defineNPENDINGCALLS 32
-struct{
-int (*func)(void*);
-void*arg;
- } calls[NPENDINGCALLS];
-intfirst;
-intlast;
-};
-
 struct_ceval_state{
 /* This single variable consolidates all requests to break out of
  the fast path in the eval loop. */

Include/internal/pycore_pystate.h

@@ -60,14 +60,6 @@ _Py_ThreadCanHandleSignals(PyInterpreterState *interp)
 }
 
 
-/* Only execute pending calls on the main thread. */
-staticinlineint
-_Py_ThreadCanHandlePendingCalls(void)
-{
-return_Py_IsMainThread();
-}
-
-
 /* Variable and static inline functions for in-line access to current thread
  and interpreter state */
 

Lib/test/support/threading_helper.py

@@ -115,7 +115,11 @@ def join_thread(thread, timeout=None):
 
 @contextlib.contextmanager
 defstart_threads(threads, unlock=None):
-importfaulthandler
+try:
+importfaulthandler
+exceptImportError:
+# It isn't supported on subinterpreters yet.
+faulthandler=None
 threads=list(threads)
 started= []
 try:
@@ -147,7 +151,8 @@ def start_threads(threads, unlock=None):
 finally:
 started= [tfortinstartedift.is_alive()]
 ifstarted:
-faulthandler.dump_traceback(sys.stdout)
+iffaulthandlerisnotNone:
+faulthandler.dump_traceback(sys.stdout)
 raiseAssertionError('Unable to join %d threads'%len(started))