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

10 files changed, 137 insertions, 174 deletions

diff --git a/Include/cpython/optimizer.h b/Include/cpython/optimizer.h
index 60b3574..744a272 100644
--- a/Include/cpython/optimizer.h
+++ b/Include/cpython/optimizer.h
@@ -142,7 +142,7 @@ void _Py_BloomFilter_Init(_PyBloomFilter *);
 void _Py_BloomFilter_Add(_PyBloomFilter *bloom, void *obj);
 PyAPI_FUNC(void) _Py_Executor_DependsOn(_PyExecutorObject *executor, void *obj);
 PyAPI_FUNC(void) _Py_Executors_InvalidateDependency(PyInterpreterState *interp, void *obj, int is_invalidation);
-extern void _Py_Executors_InvalidateAll(PyInterpreterState *interp, int is_invalidation);
+PyAPI_FUNC(void) _Py_Executors_InvalidateAll(PyInterpreterState *interp, int is_invalidation);
 
 /* For testing */
 PyAPI_FUNC(PyObject *)PyUnstable_Optimizer_NewCounter(void);
diff --git a/Include/internal/pycore_opcode_metadata.h b/Include/internal/pycore_opcode_metadata.h
index 808bade..d10224c 100644
--- a/Include/internal/pycore_opcode_metadata.h
+++ b/Include/internal/pycore_opcode_metadata.h
@@ -1029,7 +1029,7 @@ const struct opcode_metadata _PyOpcode_opcode_metadata[268] = {
     [END_ASYNC_FOR] = { true, INSTR_FMT_IX, HAS_ERROR_FLAG | HAS_ERROR_NO_POP_FLAG | HAS_ESCAPES_FLAG },
     [END_FOR] = { true, INSTR_FMT_IX, HAS_PURE_FLAG },
     [END_SEND] = { true, INSTR_FMT_IX, HAS_PURE_FLAG },
-    [ENTER_EXECUTOR] = { true, INSTR_FMT_IB, HAS_ARG_FLAG | HAS_EVAL_BREAK_FLAG },
+    [ENTER_EXECUTOR] = { true, INSTR_FMT_IB, HAS_ARG_FLAG },
     [EXIT_INIT_CHECK] = { true, INSTR_FMT_IX, HAS_ERROR_FLAG | HAS_ERROR_NO_POP_FLAG | HAS_ESCAPES_FLAG },
     [EXTENDED_ARG] = { true, INSTR_FMT_IB, HAS_ARG_FLAG },
     [FORMAT_SIMPLE] = { true, INSTR_FMT_IX, HAS_ERROR_FLAG | HAS_ESCAPES_FLAG },
diff --git a/Include/internal/pycore_uop_ids.h b/Include/internal/pycore_uop_ids.h
index 0a2231e..aa39404 100644
--- a/Include/internal/pycore_uop_ids.h
+++ b/Include/internal/pycore_uop_ids.h
@@ -94,47 +94,46 @@ extern "C" {
 #define _DYNAMIC_EXIT 343
 #define _END_SEND END_SEND
 #define _ERROR_POP_N 344
-#define _EVAL_BREAKER_EXIT 345
 #define _EXIT_INIT_CHECK EXIT_INIT_CHECK
-#define _FATAL_ERROR 346
+#define _FATAL_ERROR 345
 #define _FORMAT_SIMPLE FORMAT_SIMPLE
 #define _FORMAT_WITH_SPEC FORMAT_WITH_SPEC
-#define _FOR_ITER 347
-#define _FOR_ITER_GEN_FRAME 348
-#define _FOR_ITER_TIER_TWO 349
+#define _FOR_ITER 346
+#define _FOR_ITER_GEN_FRAME 347
+#define _FOR_ITER_TIER_TWO 348
 #define _GET_AITER GET_AITER
 #define _GET_ANEXT GET_ANEXT
 #define _GET_AWAITABLE GET_AWAITABLE
 #define _GET_ITER GET_ITER
 #define _GET_LEN GET_LEN
 #define _GET_YIELD_FROM_ITER GET_YIELD_FROM_ITER
-#define _GUARD_BOTH_FLOAT 350
-#define _GUARD_BOTH_INT 351
-#define _GUARD_BOTH_UNICODE 352
-#define _GUARD_BUILTINS_VERSION 353
-#define _GUARD_DORV_NO_DICT 354
-#define _GUARD_DORV_VALUES_INST_ATTR_FROM_DICT 355
-#define _GUARD_GLOBALS_VERSION 356
-#define _GUARD_IS_FALSE_POP 357
-#define _GUARD_IS_NONE_POP 358
-#define _GUARD_IS_NOT_NONE_POP 359
-#define _GUARD_IS_TRUE_POP 360
-#define _GUARD_KEYS_VERSION 361
-#define _GUARD_NOS_FLOAT 362
-#define _GUARD_NOS_INT 363
-#define _GUARD_NOT_EXHAUSTED_LIST 364
-#define _GUARD_NOT_EXHAUSTED_RANGE 365
-#define _GUARD_NOT_EXHAUSTED_TUPLE 366
-#define _GUARD_TOS_FLOAT 367
-#define _GUARD_TOS_INT 368
-#define _GUARD_TYPE_VERSION 369
-#define _INIT_CALL_BOUND_METHOD_EXACT_ARGS 370
-#define _INIT_CALL_PY_EXACT_ARGS 371
-#define _INIT_CALL_PY_EXACT_ARGS_0 372
-#define _INIT_CALL_PY_EXACT_ARGS_1 373
-#define _INIT_CALL_PY_EXACT_ARGS_2 374
-#define _INIT_CALL_PY_EXACT_ARGS_3 375
-#define _INIT_CALL_PY_EXACT_ARGS_4 376
+#define _GUARD_BOTH_FLOAT 349
+#define _GUARD_BOTH_INT 350
+#define _GUARD_BOTH_UNICODE 351
+#define _GUARD_BUILTINS_VERSION 352
+#define _GUARD_DORV_NO_DICT 353
+#define _GUARD_DORV_VALUES_INST_ATTR_FROM_DICT 354
+#define _GUARD_GLOBALS_VERSION 355
+#define _GUARD_IS_FALSE_POP 356
+#define _GUARD_IS_NONE_POP 357
+#define _GUARD_IS_NOT_NONE_POP 358
+#define _GUARD_IS_TRUE_POP 359
+#define _GUARD_KEYS_VERSION 360
+#define _GUARD_NOS_FLOAT 361
+#define _GUARD_NOS_INT 362
+#define _GUARD_NOT_EXHAUSTED_LIST 363
+#define _GUARD_NOT_EXHAUSTED_RANGE 364
+#define _GUARD_NOT_EXHAUSTED_TUPLE 365
+#define _GUARD_TOS_FLOAT 366
+#define _GUARD_TOS_INT 367
+#define _GUARD_TYPE_VERSION 368
+#define _INIT_CALL_BOUND_METHOD_EXACT_ARGS 369
+#define _INIT_CALL_PY_EXACT_ARGS 370
+#define _INIT_CALL_PY_EXACT_ARGS_0 371
+#define _INIT_CALL_PY_EXACT_ARGS_1 372
+#define _INIT_CALL_PY_EXACT_ARGS_2 373
+#define _INIT_CALL_PY_EXACT_ARGS_3 374
+#define _INIT_CALL_PY_EXACT_ARGS_4 375
 #define _INSTRUMENTED_CALL INSTRUMENTED_CALL
 #define _INSTRUMENTED_CALL_FUNCTION_EX INSTRUMENTED_CALL_FUNCTION_EX
 #define _INSTRUMENTED_CALL_KW INSTRUMENTED_CALL_KW
@@ -151,65 +150,65 @@ extern "C" {
 #define _INSTRUMENTED_RETURN_CONST INSTRUMENTED_RETURN_CONST
 #define _INSTRUMENTED_RETURN_VALUE INSTRUMENTED_RETURN_VALUE
 #define _INSTRUMENTED_YIELD_VALUE INSTRUMENTED_YIELD_VALUE
-#define _INTERNAL_INCREMENT_OPT_COUNTER 377
-#define _IS_NONE 378
+#define _INTERNAL_INCREMENT_OPT_COUNTER 376
+#define _IS_NONE 377
 #define _IS_OP IS_OP
-#define _ITER_CHECK_LIST 379
-#define _ITER_CHECK_RANGE 380
-#define _ITER_CHECK_TUPLE 381
-#define _ITER_JUMP_LIST 382
-#define _ITER_JUMP_RANGE 383
-#define _ITER_JUMP_TUPLE 384
-#define _ITER_NEXT_LIST 385
-#define _ITER_NEXT_RANGE 386
-#define _ITER_NEXT_TUPLE 387
-#define _JUMP_TO_TOP 388
+#define _ITER_CHECK_LIST 378
+#define _ITER_CHECK_RANGE 379
+#define _ITER_CHECK_TUPLE 380
+#define _ITER_JUMP_LIST 381
+#define _ITER_JUMP_RANGE 382
+#define _ITER_JUMP_TUPLE 383
+#define _ITER_NEXT_LIST 384
+#define _ITER_NEXT_RANGE 385
+#define _ITER_NEXT_TUPLE 386
+#define _JUMP_TO_TOP 387
 #define _LIST_APPEND LIST_APPEND
 #define _LIST_EXTEND LIST_EXTEND
 #define _LOAD_ASSERTION_ERROR LOAD_ASSERTION_ERROR
-#define _LOAD_ATTR 389
-#define _LOAD_ATTR_CLASS 390
-#define _LOAD_ATTR_CLASS_0 391
-#define _LOAD_ATTR_CLASS_1 392
+#define _LOAD_ATTR 388
+#define _LOAD_ATTR_CLASS 389
+#define _LOAD_ATTR_CLASS_0 390
+#define _LOAD_ATTR_CLASS_1 391
 #define _LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN LOAD_ATTR_GETATTRIBUTE_OVERRIDDEN
-#define _LOAD_ATTR_INSTANCE_VALUE 393
-#define _LOAD_ATTR_INSTANCE_VALUE_0 394
-#define _LOAD_ATTR_INSTANCE_VALUE_1 395
-#define _LOAD_ATTR_METHOD_LAZY_DICT 396
-#define _LOAD_ATTR_METHOD_NO_DICT 397
-#define _LOAD_ATTR_METHOD_WITH_VALUES 398
-#define _LOAD_ATTR_MODULE 399
-#define _LOAD_ATTR_NONDESCRIPTOR_NO_DICT 400
-#define _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES 401
+#define _LOAD_ATTR_INSTANCE_VALUE 392
+#define _LOAD_ATTR_INSTANCE_VALUE_0 393
+#define _LOAD_ATTR_INSTANCE_VALUE_1 394
+#define _LOAD_ATTR_METHOD_LAZY_DICT 395
+#define _LOAD_ATTR_METHOD_NO_DICT 396
+#define _LOAD_ATTR_METHOD_WITH_VALUES 397
+#define _LOAD_ATTR_MODULE 398
+#define _LOAD_ATTR_NONDESCRIPTOR_NO_DICT 399
+#define _LOAD_ATTR_NONDESCRIPTOR_WITH_VALUES 400
 #define _LOAD_ATTR_PROPERTY LOAD_ATTR_PROPERTY
-#define _LOAD_ATTR_SLOT 402
-#define _LOAD_ATTR_SLOT_0 403
-#define _LOAD_ATTR_SLOT_1 404
-#define _LOAD_ATTR_WITH_HINT 405
+#define _LOAD_ATTR_SLOT 401
+#define _LOAD_ATTR_SLOT_0 402
+#define _LOAD_ATTR_SLOT_1 403
+#define _LOAD_ATTR_WITH_HINT 404
 #define _LOAD_BUILD_CLASS LOAD_BUILD_CLASS
 #define _LOAD_CONST LOAD_CONST
-#define _LOAD_CONST_INLINE 406
-#define _LOAD_CONST_INLINE_BORROW 407
-#define _LOAD_CONST_INLINE_BORROW_WITH_NULL 408
-#define _LOAD_CONST_INLINE_WITH_NULL 409
+#define _LOAD_CONST_INLINE 405
+#define _LOAD_CONST_INLINE_BORROW 406
+#define _LOAD_CONST_INLINE_BORROW_WITH_NULL 407
+#define _LOAD_CONST_INLINE_WITH_NULL 408
 #define _LOAD_DEREF LOAD_DEREF
-#define _LOAD_FAST 410
-#define _LOAD_FAST_0 411
-#define _LOAD_FAST_1 412
-#define _LOAD_FAST_2 413
-#define _LOAD_FAST_3 414
-#define _LOAD_FAST_4 415
-#define _LOAD_FAST_5 416
-#define _LOAD_FAST_6 417
-#define _LOAD_FAST_7 418
+#define _LOAD_FAST 409
+#define _LOAD_FAST_0 410
+#define _LOAD_FAST_1 411
+#define _LOAD_FAST_2 412
+#define _LOAD_FAST_3 413
+#define _LOAD_FAST_4 414
+#define _LOAD_FAST_5 415
+#define _LOAD_FAST_6 416
+#define _LOAD_FAST_7 417
 #define _LOAD_FAST_AND_CLEAR LOAD_FAST_AND_CLEAR
 #define _LOAD_FAST_CHECK LOAD_FAST_CHECK
 #define _LOAD_FAST_LOAD_FAST LOAD_FAST_LOAD_FAST
 #define _LOAD_FROM_DICT_OR_DEREF LOAD_FROM_DICT_OR_DEREF
 #define _LOAD_FROM_DICT_OR_GLOBALS LOAD_FROM_DICT_OR_GLOBALS
-#define _LOAD_GLOBAL 419
-#define _LOAD_GLOBAL_BUILTINS 420
-#define _LOAD_GLOBAL_MODULE 421
+#define _LOAD_GLOBAL 418
+#define _LOAD_GLOBAL_BUILTINS 419
+#define _LOAD_GLOBAL_MODULE 420
 #define _LOAD_LOCALS LOAD_LOCALS
 #define _LOAD_NAME LOAD_NAME
 #define _LOAD_SUPER_ATTR_ATTR LOAD_SUPER_ATTR_ATTR
@@ -223,51 +222,51 @@ extern "C" {
 #define _MATCH_SEQUENCE MATCH_SEQUENCE
 #define _NOP NOP
 #define _POP_EXCEPT POP_EXCEPT
-#define _POP_FRAME 422
-#define _POP_JUMP_IF_FALSE 423
-#define _POP_JUMP_IF_TRUE 424
+#define _POP_FRAME 421
+#define _POP_JUMP_IF_FALSE 422
+#define _POP_JUMP_IF_TRUE 423
 #define _POP_TOP POP_TOP
-#define _POP_TOP_LOAD_CONST_INLINE_BORROW 425
+#define _POP_TOP_LOAD_CONST_INLINE_BORROW 424
 #define _PUSH_EXC_INFO PUSH_EXC_INFO
-#define _PUSH_FRAME 426
+#define _PUSH_FRAME 425
 #define _PUSH_NULL PUSH_NULL
-#define _REPLACE_WITH_TRUE 427
+#define _REPLACE_WITH_TRUE 426
 #define _RESUME_CHECK RESUME_CHECK
 #define _RETURN_GENERATOR RETURN_GENERATOR
-#define _SAVE_RETURN_OFFSET 428
-#define _SEND 429
+#define _SAVE_RETURN_OFFSET 427
+#define _SEND 428
 #define _SEND_GEN SEND_GEN
 #define _SETUP_ANNOTATIONS SETUP_ANNOTATIONS
 #define _SET_ADD SET_ADD
 #define _SET_FUNCTION_ATTRIBUTE SET_FUNCTION_ATTRIBUTE
 #define _SET_UPDATE SET_UPDATE
-#define _SIDE_EXIT 430
-#define _START_EXECUTOR 431
-#define _STORE_ATTR 432
-#define _STORE_ATTR_INSTANCE_VALUE 433
-#define _STORE_ATTR_SLOT 434
+#define _SIDE_EXIT 429
+#define _START_EXECUTOR 430
+#define _STORE_ATTR 431
+#define _STORE_ATTR_INSTANCE_VALUE 432
+#define _STORE_ATTR_SLOT 433
 #define _STORE_ATTR_WITH_HINT STORE_ATTR_WITH_HINT
 #define _STORE_DEREF STORE_DEREF
-#define _STORE_FAST 435
-#define _STORE_FAST_0 436
-#define _STORE_FAST_1 437
-#define _STORE_FAST_2 438
-#define _STORE_FAST_3 439
-#define _STORE_FAST_4 440
-#define _STORE_FAST_5 441
-#define _STORE_FAST_6 442
-#define _STORE_FAST_7 443
+#define _STORE_FAST 434
+#define _STORE_FAST_0 435
+#define _STORE_FAST_1 436
+#define _STORE_FAST_2 437
+#define _STORE_FAST_3 438
+#define _STORE_FAST_4 439
+#define _STORE_FAST_5 440
+#define _STORE_FAST_6 441
+#define _STORE_FAST_7 442
 #define _STORE_FAST_LOAD_FAST STORE_FAST_LOAD_FAST
 #define _STORE_FAST_STORE_FAST STORE_FAST_STORE_FAST
 #define _STORE_GLOBAL STORE_GLOBAL
 #define _STORE_NAME STORE_NAME
 #define _STORE_SLICE STORE_SLICE
-#define _STORE_SUBSCR 444
+#define _STORE_SUBSCR 443
 #define _STORE_SUBSCR_DICT STORE_SUBSCR_DICT
 #define _STORE_SUBSCR_LIST_INT STORE_SUBSCR_LIST_INT
 #define _SWAP SWAP
-#define _TIER2_RESUME_CHECK 445
-#define _TO_BOOL 446
+#define _TIER2_RESUME_CHECK 444
+#define _TO_BOOL 445
 #define _TO_BOOL_BOOL TO_BOOL_BOOL
 #define _TO_BOOL_INT TO_BOOL_INT
 #define _TO_BOOL_LIST TO_BOOL_LIST
@@ -277,13 +276,13 @@ extern "C" {
 #define _UNARY_NEGATIVE UNARY_NEGATIVE
 #define _UNARY_NOT UNARY_NOT
 #define _UNPACK_EX UNPACK_EX
-#define _UNPACK_SEQUENCE 447
+#define _UNPACK_SEQUENCE 446
 #define _UNPACK_SEQUENCE_LIST UNPACK_SEQUENCE_LIST
 #define _UNPACK_SEQUENCE_TUPLE UNPACK_SEQUENCE_TUPLE
 #define _UNPACK_SEQUENCE_TWO_TUPLE UNPACK_SEQUENCE_TWO_TUPLE
 #define _WITH_EXCEPT_START WITH_EXCEPT_START
 #define _YIELD_VALUE YIELD_VALUE
-#define MAX_UOP_ID 447
+#define MAX_UOP_ID 446
 
 #ifdef __cplusplus
 }
diff --git a/Include/internal/pycore_uop_metadata.h b/Include/internal/pycore_uop_metadata.h
index 5697b13..d086002 100644
--- a/Include/internal/pycore_uop_metadata.h
+++ b/Include/internal/pycore_uop_metadata.h
@@ -233,7 +233,7 @@ const uint16_t _PyUop_Flags[MAX_UOP_ID+1] = {
     [_GUARD_IS_FALSE_POP] = HAS_EXIT_FLAG,
     [_GUARD_IS_NONE_POP] = HAS_EXIT_FLAG,
     [_GUARD_IS_NOT_NONE_POP] = HAS_EXIT_FLAG,
-    [_JUMP_TO_TOP] = HAS_EVAL_BREAK_FLAG,
+    [_JUMP_TO_TOP] = 0,
     [_SET_IP] = 0,
     [_CHECK_STACK_SPACE_OPERAND] = HAS_DEOPT_FLAG,
     [_SAVE_RETURN_OFFSET] = HAS_ARG_FLAG,
@@ -254,8 +254,7 @@ const uint16_t _PyUop_Flags[MAX_UOP_ID+1] = {
     [_DEOPT] = 0,
     [_SIDE_EXIT] = 0,
     [_ERROR_POP_N] = HAS_ARG_FLAG,
-    [_TIER2_RESUME_CHECK] = HAS_EXIT_FLAG,
-    [_EVAL_BREAKER_EXIT] = HAS_ESCAPES_FLAG,
+    [_TIER2_RESUME_CHECK] = HAS_DEOPT_FLAG,
 };
 
 const uint8_t _PyUop_Replication[MAX_UOP_ID+1] = {
@@ -339,7 +338,6 @@ const char *const _PyOpcode_uop_name[MAX_UOP_ID+1] = {
     [_DYNAMIC_EXIT] = "_DYNAMIC_EXIT",
     [_END_SEND] = "_END_SEND",
     [_ERROR_POP_N] = "_ERROR_POP_N",
-    [_EVAL_BREAKER_EXIT] = "_EVAL_BREAKER_EXIT",
     [_EXIT_INIT_CHECK] = "_EXIT_INIT_CHECK",
     [_EXIT_TRACE] = "_EXIT_TRACE",
     [_FATAL_ERROR] = "_FATAL_ERROR",
@@ -978,8 +976,6 @@ int _PyUop_num_popped(int opcode, int oparg)
             return oparg;
         case _TIER2_RESUME_CHECK:
             return 0;
-        case _EVAL_BREAKER_EXIT:
-            return 0;
         default:
             return -1;
     }
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 //
 
     }
diff --git a/Python/executor_cases.c.h b/Python/executor_cases.c.h
index b17f376..f97f279 100644
--- a/Python/executor_cases.c.h
+++ b/Python/executor_cases.c.h
@@ -4094,7 +4094,6 @@
             #ifndef _Py_JIT
             next_uop = &current_executor->trace[1];
             #endif
-            CHECK_EVAL_BREAKER();
             break;
         }
 
@@ -4353,14 +4352,4 @@
             break;
         }
 
-        case _EVAL_BREAKER_EXIT: {
-            _Py_CHECK_EMSCRIPTEN_SIGNALS_PERIODICALLY();
-            QSBR_QUIESCENT_STATE(tstate);
-            if (_Py_HandlePending(tstate) != 0) {
-                GOTO_UNWIND();
-            }
-            EXIT_TO_TRACE();
-            break;
-        }
-
 #undef TIER_TWO
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);
diff --git a/Python/optimizer.c b/Python/optimizer.c
index 2389338..0509473 100644
--- a/Python/optimizer.c
+++ b/Python/optimizer.c
@@ -627,6 +627,9 @@ top:  // Jump here after _PUSH_FRAME or likely branches
             if (opcode == JUMP_BACKWARD || opcode == JUMP_BACKWARD_NO_INTERRUPT) {
                 instr += 1 + _PyOpcode_Caches[opcode] - (int32_t)oparg;
                 initial_instr = instr;
+                if (opcode == JUMP_BACKWARD) {
+                    ADD_TO_TRACE(_TIER2_RESUME_CHECK, 0, 0, target);
+                }
                 continue;
             }
             else {
@@ -976,6 +979,7 @@ prepare_for_execution(_PyUOpInstruction *buffer, int length)
     int32_t current_error = -1;
     int32_t current_error_target = -1;
     int32_t current_popped = -1;
+    int32_t current_exit_op = -1;
     /* Leaving in NOPs slows down the interpreter and messes up the stats */
     _PyUOpInstruction *copy_to = &buffer[0];
     for (int i = 0; i < length; i++) {
@@ -994,20 +998,11 @@ prepare_for_execution(_PyUOpInstruction *buffer, int length)
         int opcode = inst->opcode;
         int32_t target = (int32_t)uop_get_target(inst);
         if (_PyUop_Flags[opcode] & (HAS_EXIT_FLAG | HAS_DEOPT_FLAG)) {
-            if (target != current_jump_target) {
-                uint16_t exit_op;
-                if (_PyUop_Flags[opcode] & HAS_EXIT_FLAG) {
-                    if (opcode == _TIER2_RESUME_CHECK) {
-                        exit_op = _EVAL_BREAKER_EXIT;
-                    }
-                    else {
-                        exit_op = _SIDE_EXIT;
-                    }
-                }
-                else {
-                    exit_op = _DEOPT;
-                }
+            uint16_t exit_op = (_PyUop_Flags[opcode] & HAS_EXIT_FLAG) ?
+                _SIDE_EXIT : _DEOPT;
+            if (target != current_jump_target || current_exit_op != exit_op) {
                 make_exit(&buffer[next_spare], exit_op, target);
+                current_exit_op = exit_op;
                 current_jump_target = target;
                 current_jump = next_spare;
                 next_spare++;
@@ -1114,7 +1109,6 @@ sanity_check(_PyExecutorObject *executor)
         CHECK(
             opcode == _DEOPT ||
             opcode == _SIDE_EXIT ||
-            opcode == _EVAL_BREAKER_EXIT ||
             opcode == _ERROR_POP_N);
         if (opcode == _SIDE_EXIT) {
             CHECK(inst->format == UOP_FORMAT_EXIT);
diff --git a/Python/optimizer_cases.c.h b/Python/optimizer_cases.c.h
index 0b69692..e680d76 100644
--- a/Python/optimizer_cases.c.h
+++ b/Python/optimizer_cases.c.h
@@ -2153,7 +2153,3 @@
             break;
         }
 
-        case _EVAL_BREAKER_EXIT: {
-            break;
-        }
-
diff --git a/Tools/jit/template.c b/Tools/jit/template.c
index 0dd0744..a81e866 100644
--- a/Tools/jit/template.c
+++ b/Tools/jit/template.c
@@ -106,7 +106,6 @@ _JIT_ENTRY(_PyInterpreterFrame *frame, PyObject **stack_pointer, PyThreadState *
 
     // The actual instruction definitions (only one will be used):
     if (uopcode == _JUMP_TO_TOP) {
-        CHECK_EVAL_BREAKER();
         PATCH_JUMP(_JIT_TOP);
     }
     switch (uopcode) {