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gh-128807: Add marking phase for free-threaded cyclic GC #128808

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Merged
nascheme merged 20 commits into from
Jan 15, 2025
Merged

gh-128807: Add marking phase for free-threaded cyclic GC #128808

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a111bff
wip: gc mark alive for nogil
nascheme Jan 8, 2025
200b69b
wip: mark more roots
nascheme Jan 14, 2025
713689a
wip: log gc timing to temp file
nascheme Jan 14, 2025
2635fe0
wip: mark stack refs as alive
nascheme Jan 14, 2025
72128e2
wip: include # of collected in debug log
nascheme Jan 14, 2025
942f77d
wip: move freeze_used to gc state
nascheme Jan 14, 2025
a3089e5
wip: fix OOM error handling, add ifdef toggles
nascheme Jan 14, 2025
4f99de6
wip: fix reversion on mark_heap_visitor()
nascheme Jan 14, 2025
4f6e539
wip: revert changes to gc_should_collect()
nascheme Jan 14, 2025
b99f2df
wip: removing timing code
nascheme Jan 14, 2025
5f6ab4c
wip: code cleanup, small bug fix
nascheme Jan 14, 2025
bd46b5f
wip: untrack tuples in "mark alive" pass
nascheme Jan 14, 2025
d25cb4a
wip: enable stacks and extra roots
nascheme Jan 14, 2025
347db45
wip: add helper gc_maybe_untrack()
nascheme Jan 14, 2025
680f80f
Add NEWS entry.
nascheme Jan 14, 2025
0c173c9
wip: spelling fixes, minor code cleanup
nascheme Jan 14, 2025
6654424
Merge branch 'origin/main' into nogil-gc-mark-alive
nascheme Jan 14, 2025
79ea47e
wip: use -1 for error convention for functions
nascheme Jan 14, 2025
0090365
wip: improve error handling for OOM
nascheme Jan 14, 2025
6100691
Add comment about gc.freeze() disabling marking.
nascheme Jan 14, 2025
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wip: mark more roots
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@nascheme
nascheme committed Jan 14, 2025
commit 200b69b12591326646a7e6d85e2296f267e73982
50 changes: 38 additions & 12 deletions Python/gc_free_threading.c
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Original file line number Diff line number Diff line change
Expand Up @@ -949,22 +949,38 @@ visit_propagate_alive(PyObject *op, _PyObjectStack *stack)
}

static int
propagate_alive_bits(PyObject *op)
propagate_alive_bits(_PyObjectStack *stack)
{
_PyObjectStack stack = { NULL };
do {
for (;;) {
PyObject *op = _PyObjectStack_Pop(stack);
if (op == NULL) {
break;
}
assert(_PyObject_GC_IS_TRACKED(op));
assert(gc_is_alive(op));
traverseproc traverse = Py_TYPE(op)->tp_traverse;
if (traverse(op, (visitproc)&visit_propagate_alive, &stack) < 0) {
_PyObjectStack_Clear(&stack);
if (traverse(op, (visitproc)&visit_propagate_alive, stack) < 0) {
_PyObjectStack_Clear(stack);
return -1;
}
op = _PyObjectStack_Pop(&stack);
} while (op != NULL);
}
return 0;
}

static bool
mark_stack_push(_PyObjectStack *stack, PyObject *op)
{
if (op == NULL) {
return true;
}
assert(!gc_is_alive(op));
gc_set_alive(op);
if (_PyObjectStack_Push(stack, Py_NewRef(op)) < 0) {
return false;
}
return true;
}

static int
mark_root_reachable(PyInterpreterState *interp,
struct collection_state *state)
Expand All @@ -978,10 +994,20 @@ mark_root_reachable(PyInterpreterState *interp,
// Check that all objects don't have ALIVE bits set
gc_visit_heaps(interp, &validate_alive_bits, &state->base);
#endif
PyObject *root = interp->sysdict;
assert(!gc_is_alive(root));
gc_set_alive(root);
propagate_alive_bits(root);
_PyObjectStack stack = { NULL };
mark_stack_push(&stack, interp->sysdict);
mark_stack_push(&stack, interp->builtins);
mark_stack_push(&stack, interp->dict);
struct types_state *types = &interp->types;
for (int i = 0; i < _Py_MAX_MANAGED_STATIC_BUILTIN_TYPES; i++) {
mark_stack_push(&stack, types->builtins.initialized[i].tp_dict);
mark_stack_push(&stack, types->builtins.initialized[i].tp_subclasses);
}
for (int i = 0; i < _Py_MAX_MANAGED_STATIC_EXT_TYPES; i++) {
mark_stack_push(&stack, types->for_extensions.initialized[i].tp_dict);
mark_stack_push(&stack, types->for_extensions.initialized[i].tp_subclasses);
}
propagate_alive_bits(&stack);

#if WITH_GC_TIMING_STATS
PyTime_t t2;
Expand Down Expand Up @@ -1014,7 +1040,7 @@ deduce_unreachable_heap(PyInterpreterState *interp,
gc_visit_heaps(interp, &update_refs, &state->base);

#if WITH_GC_TIMING_STATS
//fprintf(stderr, "gc alive %d immortal %d checked %d gc %d\n", num_alive, num_immortal, num_checked, num_gc);
fprintf(stderr, "gc alive %d immortal %d checked %d gc %d\n", num_alive, num_immortal, num_checked, num_gc);
#endif

#ifdef GC_DEBUG
Expand Down