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

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Mark Shannon 2024-05-02 13:10:31 +01:00 • committed by GitHub
parent f8e088df2a
commit 67bba9dd0f
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10 changed files with 137 additions and 174 deletions
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38
Python/bytecodes.c
View file

@ -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 //
}

11
Python/executor_cases.c.h generated
View file

@ -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

16
Python/generated_cases.c.h generated
View file

@ -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);

22
Python/optimizer.c
View file

@ -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);

4
Python/optimizer_cases.c.h generated
View file

@ -2153,7 +2153,3 @@
break;
}
case _EVAL_BREAKER_EXIT: {
break;
}