GH-117442: Check eval-breaker at start (rather than end) of tier 2 loops (GH-118482)

1 files changed, 9 insertions, 7 deletions

diff --git a/Python/generated_cases.c.h b/Python/generated_cases.c.h
index 32b485e..2a0f268 100644
--- a/Python/generated_cases.c.h
+++ b/Python/generated_cases.c.h
@@ -2493,19 +2493,21 @@
             next_instr += 1;
             INSTRUCTION_STATS(ENTER_EXECUTOR);
             #ifdef _Py_TIER2
-            int prevoparg = oparg;
-            CHECK_EVAL_BREAKER();
-            if (this_instr->op.code != ENTER_EXECUTOR ||
-                this_instr->op.arg != prevoparg) {
-                next_instr = this_instr;
-                DISPATCH();
-            }
             PyCodeObject *code = _PyFrame_GetCode(frame);
             _PyExecutorObject *executor = code->co_executors->executors[oparg & 255];
             assert(executor->vm_data.index == INSTR_OFFSET() - 1);
             assert(executor->vm_data.code == code);
             assert(executor->vm_data.valid);
             assert(tstate->previous_executor == NULL);
+            /* If the eval breaker is set then stay in tier 1.
+             * This avoids any potentially infinite loops
+             * involving _RESUME_CHECK */
+            if (_Py_atomic_load_uintptr_relaxed(&tstate->eval_breaker) & _PY_EVAL_EVENTS_MASK) {
+                opcode = executor->vm_data.opcode;
+                oparg = (oparg & ~255) | executor->vm_data.oparg;
+                next_instr = this_instr;
+                DISPATCH_GOTO();
+            }
             tstate->previous_executor = Py_None;
             Py_INCREF(executor);
             GOTO_TIER_TWO(executor);