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gh-120321: Make gi_frame_state transitions atomic in FT build (gh-142599)

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This makes generator frame state transitions atomic in the free
threading build, which avoids segfaults when trying to execute
a generator from multiple threads concurrently.

There are still a few operations that aren't thread-safe and may crash
if performed concurrently on the same generator/coroutine:

 * Accessing gi_yieldfrom/cr_await/ag_await
 * Accessing gi_frame/cr_frame/ag_frame
 * Async generator operations
This commit is contained in:
Sam Gross 2025-12-19 14:10:37 -05:00 • committed by GitHub
parent e2a7db7175
commit 08bc03ff2a
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GPG key ID: B5690EEEBB952194
16 changed files with 1124 additions and 883 deletions
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22
Python/generated_cases.c.h generated
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@ -5548,14 +5548,7 @@
assert(_PyOpcode_Deopt[opcode] == (FOR_ITER));
JUMP_TO_PREDICTED(FOR_ITER);
}
#ifdef Py_GIL_DISABLED
if (!_PyObject_IsUniquelyReferenced((PyObject *)gen)) {
UPDATE_MISS_STATS(FOR_ITER);
assert(_PyOpcode_Deopt[opcode] == (FOR_ITER));
JUMP_TO_PREDICTED(FOR_ITER);
}
#endif
if (gen->gi_frame_state >= FRAME_EXECUTING) {
if (!gen_try_set_executing((PyGenObject *)gen)) {
UPDATE_MISS_STATS(FOR_ITER);
assert(_PyOpcode_Deopt[opcode] == (FOR_ITER));
JUMP_TO_PREDICTED(FOR_ITER);
@ -5563,7 +5556,6 @@
STAT_INC(FOR_ITER, hit);
_PyInterpreterFrame *pushed_frame = &gen->gi_iframe;
_PyFrame_StackPush(pushed_frame, PyStackRef_None);
gen->gi_frame_state = FRAME_EXECUTING;
gen->gi_exc_state.previous_item = tstate->exc_info;
tstate->exc_info = &gen->gi_exc_state;
pushed_frame->previous = frame;
@ -7327,7 +7319,6 @@
PyGenObject *gen = _PyGen_GetGeneratorFromFrame(frame);
assert(FRAME_SUSPENDED_YIELD_FROM == FRAME_SUSPENDED + 1);
assert(oparg == 0 || oparg == 1);
gen->gi_frame_state = FRAME_SUSPENDED + oparg;
_PyStackRef temp = retval;
stack_pointer += -1;
ASSERT_WITHIN_STACK_BOUNDS(__FILE__, __LINE__);
@ -7338,6 +7329,8 @@
_PyInterpreterFrame *gen_frame = frame;
frame = tstate->current_frame = frame->previous;
gen_frame->previous = NULL;
((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_YIELD;
FT_ATOMIC_STORE_INT8_RELEASE(gen->gi_frame_state, FRAME_SUSPENDED + oparg);
assert(INLINE_CACHE_ENTRIES_SEND == INLINE_CACHE_ENTRIES_FOR_ITER);
#if TIER_ONE
assert(frame->instr_ptr->op.code == INSTRUMENTED_LINE ||
@ -10301,14 +10294,13 @@
assert(frame->owner != FRAME_OWNED_BY_INTERPRETER);
if ((tstate->interp->eval_frame == NULL) &&
(Py_TYPE(receiver_o) == &PyGen_Type || Py_TYPE(receiver_o) == &PyCoro_Type) &&
((PyGenObject *)receiver_o)->gi_frame_state < FRAME_EXECUTING)
gen_try_set_executing((PyGenObject *)receiver_o))
{
PyGenObject *gen = (PyGenObject *)receiver_o;
_PyInterpreterFrame *gen_frame = &gen->gi_iframe;
_PyFrame_StackPush(gen_frame, PyStackRef_MakeHeapSafe(v));
stack_pointer += -1;
ASSERT_WITHIN_STACK_BOUNDS(__FILE__, __LINE__);
gen->gi_frame_state = FRAME_EXECUTING;
gen->gi_exc_state.previous_item = tstate->exc_info;
tstate->exc_info = &gen->gi_exc_state;
assert( 2u + oparg <= UINT16_MAX);
@ -10401,7 +10393,7 @@
assert(_PyOpcode_Deopt[opcode] == (SEND));
JUMP_TO_PREDICTED(SEND);
}
if (gen->gi_frame_state >= FRAME_EXECUTING) {
if (!gen_try_set_executing((PyGenObject *)gen)) {
UPDATE_MISS_STATS(SEND);
assert(_PyOpcode_Deopt[opcode] == (SEND));
JUMP_TO_PREDICTED(SEND);
@ -10409,7 +10401,6 @@
STAT_INC(SEND, hit);
_PyInterpreterFrame *pushed_frame = &gen->gi_iframe;
_PyFrame_StackPush(pushed_frame, PyStackRef_MakeHeapSafe(v));
gen->gi_frame_state = FRAME_EXECUTING;
gen->gi_exc_state.previous_item = tstate->exc_info;
tstate->exc_info = &gen->gi_exc_state;
assert( 2u + oparg <= UINT16_MAX);
@ -12045,7 +12036,6 @@
PyGenObject *gen = _PyGen_GetGeneratorFromFrame(frame);
assert(FRAME_SUSPENDED_YIELD_FROM == FRAME_SUSPENDED + 1);
assert(oparg == 0 || oparg == 1);
gen->gi_frame_state = FRAME_SUSPENDED + oparg;
_PyStackRef temp = retval;
stack_pointer += -1;
ASSERT_WITHIN_STACK_BOUNDS(__FILE__, __LINE__);
@ -12056,6 +12046,8 @@
_PyInterpreterFrame *gen_frame = frame;
frame = tstate->current_frame = frame->previous;
gen_frame->previous = NULL;
((_PyThreadStateImpl *)tstate)->generator_return_kind = GENERATOR_YIELD;
FT_ATOMIC_STORE_INT8_RELEASE(gen->gi_frame_state, FRAME_SUSPENDED + oparg);
assert(INLINE_CACHE_ENTRIES_SEND == INLINE_CACHE_ENTRIES_FOR_ITER);
#if TIER_ONE
assert(frame->instr_ptr->op.code == INSTRUMENTED_LINE ||