1 files changed, 13 insertions, 25 deletions

diff --git a/Python/bytecodes.c b/Python/bytecodes.c
index 002b5a3..b1be40d 100644
--- a/Python/bytecodes.c
+++ b/Python/bytecodes.c
@@ -2410,20 +2410,21 @@ dummy_func(
 
         tier1 inst(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);
@@ -4111,7 +4112,6 @@ dummy_func(
 #ifndef _Py_JIT
             next_uop = &current_executor->trace[1];
 #endif
-            CHECK_EVAL_BREAKER();
         }
 
         tier2 op(_SET_IP, (instr_ptr/4 --)) {
@@ -4277,30 +4277,18 @@ dummy_func(
             GOTO_UNWIND();
         }
 
-
-        /* Special version of RESUME_CHECK that (when paired with _EVAL_BREAKER_EXIT)
-         * is safe for tier 2. Progress is guaranteed because _EVAL_BREAKER_EXIT calls
-         * _Py_HandlePending which clears the eval_breaker so that _TIER2_RESUME_CHECK
-         * will not exit if it is immediately executed again. */
+        /* Progress is guaranteed if we DEOPT on the eval breaker, because
+         * ENTER_EXECUTOR will not re-enter tier 2 with the eval breaker set. */
         tier2 op(_TIER2_RESUME_CHECK, (--)) {
 #if defined(__EMSCRIPTEN__)
-            EXIT_IF(_Py_emscripten_signal_clock == 0);
+            DEOPT_IF(_Py_emscripten_signal_clock == 0);
             _Py_emscripten_signal_clock -= Py_EMSCRIPTEN_SIGNAL_HANDLING;
 #endif
             uintptr_t eval_breaker = _Py_atomic_load_uintptr_relaxed(&tstate->eval_breaker);
-            EXIT_IF(eval_breaker & _PY_EVAL_EVENTS_MASK);
+            DEOPT_IF(eval_breaker & _PY_EVAL_EVENTS_MASK);
             assert(eval_breaker == FT_ATOMIC_LOAD_UINTPTR_ACQUIRE(_PyFrame_GetCode(frame)->_co_instrumentation_version));
         }
 
-        tier2 op(_EVAL_BREAKER_EXIT, (--)) {
-            _Py_CHECK_EMSCRIPTEN_SIGNALS_PERIODICALLY();
-            QSBR_QUIESCENT_STATE(tstate);
-            if (_Py_HandlePending(tstate) != 0) {
-                GOTO_UNWIND();
-            }
-            EXIT_TO_TRACE();
-        }
-
 // END BYTECODES //
 
     }