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GH-117760: Streamline the trashcan mechanism (GH-117763)

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Mark Shannon 2024-04-17 11:08:05 +01:00 • committed by GitHub
parent c917b3e8e1
commit 147cd0581e
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5 changed files with 44 additions and 129 deletions
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114
Objects/object.c
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@ -2709,33 +2709,31 @@ finally:
/* Trashcan support. */
#define _PyTrash_UNWIND_LEVEL 50
/* Add op to the gcstate->trash_delete_later list. Called when the current
* call-stack depth gets large. op must be a currently untracked gc'ed
* object, with refcount 0. Py_DECREF must already have been called on it.
*/
static void
_PyTrash_thread_deposit_object(struct _py_trashcan *trash, PyObject *op)
void
_PyTrash_thread_deposit_object(PyThreadState *tstate, PyObject *op)
{
_PyObject_ASSERT(op, _PyObject_IS_GC(op));
_PyObject_ASSERT(op, !_PyObject_GC_IS_TRACKED(op));
_PyObject_ASSERT(op, Py_REFCNT(op) == 0);
#ifdef Py_GIL_DISABLED
_PyObject_ASSERT(op, op->ob_tid == 0);
op->ob_tid = (uintptr_t)trash->delete_later;
op->ob_tid = (uintptr_t)tstate->delete_later;
#else
_PyGCHead_SET_PREV(_Py_AS_GC(op), (PyGC_Head*)trash->delete_later);
_PyGCHead_SET_PREV(_Py_AS_GC(op), (PyGC_Head*)tstate->delete_later);
#endif
trash->delete_later = op;
tstate->delete_later = op;
}
/* Deallocate all the objects in the gcstate->trash_delete_later list.
* Called when the call-stack unwinds again. */
static void
_PyTrash_thread_destroy_chain(struct _py_trashcan *trash)
void
_PyTrash_thread_destroy_chain(PyThreadState *tstate)
{
/* We need to increase trash_delete_nesting here, otherwise,
/* We need to increase c_recursion_remaining here, otherwise,
_PyTrash_thread_destroy_chain will be called recursively
and then possibly crash. An example that may crash without
increase:
@ -2746,17 +2744,17 @@ _PyTrash_thread_destroy_chain(struct _py_trashcan *trash)
tups = [(tup,) for tup in tups]
del tups
*/
assert(trash->delete_nesting == 0);
++trash->delete_nesting;
while (trash->delete_later) {
PyObject *op = trash->delete_later;
assert(tstate->c_recursion_remaining > Py_TRASHCAN_HEADROOM);
tstate->c_recursion_remaining--;
while (tstate->delete_later) {
PyObject *op = tstate->delete_later;
destructor dealloc = Py_TYPE(op)->tp_dealloc;
#ifdef Py_GIL_DISABLED
trash->delete_later = (PyObject*) op->ob_tid;
tstate->delete_later = (PyObject*) op->ob_tid;
op->ob_tid = 0;
#else
trash->delete_later = (PyObject*) _PyGCHead_PREV(_Py_AS_GC(op));
tstate->delete_later = (PyObject*) _PyGCHead_PREV(_Py_AS_GC(op));
#endif
/* Call the deallocator directly. This used to try to
@ -2767,92 +2765,10 @@ _PyTrash_thread_destroy_chain(struct _py_trashcan *trash)
*/
_PyObject_ASSERT(op, Py_REFCNT(op) == 0);
(*dealloc)(op);
assert(trash->delete_nesting == 1);
}
--trash->delete_nesting;
tstate->c_recursion_remaining++;
}
static struct _py_trashcan *
_PyTrash_get_state(PyThreadState *tstate)
{
if (tstate != NULL) {
return &tstate->trash;
}
// The current thread must be finalizing.
// Fall back to using thread-local state.
// XXX Use thread-local variable syntax?
assert(PyThread_tss_is_created(&_PyRuntime.trashTSSkey));
struct _py_trashcan *trash =
(struct _py_trashcan *)PyThread_tss_get(&_PyRuntime.trashTSSkey);
if (trash == NULL) {
trash = PyMem_RawMalloc(sizeof(struct _py_trashcan));
if (trash == NULL) {
Py_FatalError("Out of memory");
}
PyThread_tss_set(&_PyRuntime.trashTSSkey, (void *)trash);
}
return trash;
}
static void
_PyTrash_clear_state(PyThreadState *tstate)
{
if (tstate != NULL) {
assert(tstate->trash.delete_later == NULL);
return;
}
if (PyThread_tss_is_created(&_PyRuntime.trashTSSkey)) {
struct _py_trashcan *trash =
(struct _py_trashcan *)PyThread_tss_get(&_PyRuntime.trashTSSkey);
if (trash != NULL) {
PyThread_tss_set(&_PyRuntime.trashTSSkey, (void *)NULL);
PyMem_RawFree(trash);
}
}
}
int
_PyTrash_begin(PyThreadState *tstate, PyObject *op)
{
// XXX Make sure the GIL is held.
struct _py_trashcan *trash = _PyTrash_get_state(tstate);
if (trash->delete_nesting >= _PyTrash_UNWIND_LEVEL) {
/* Store the object (to be deallocated later) and jump past
* Py_TRASHCAN_END, skipping the body of the deallocator */
_PyTrash_thread_deposit_object(trash, op);
return 1;
}
++trash->delete_nesting;
return 0;
}
void
_PyTrash_end(PyThreadState *tstate)
{
// XXX Make sure the GIL is held.
struct _py_trashcan *trash = _PyTrash_get_state(tstate);
--trash->delete_nesting;
if (trash->delete_nesting <= 0) {
if (trash->delete_later != NULL) {
_PyTrash_thread_destroy_chain(trash);
}
_PyTrash_clear_state(tstate);
}
}
/* bpo-40170: It's only be used in Py_TRASHCAN_BEGIN macro to hide
implementation details. */
int
_PyTrash_cond(PyObject *op, destructor dealloc)
{
return Py_TYPE(op)->tp_dealloc == dealloc;
}
void _Py_NO_RETURN
_PyObject_AssertFailed(PyObject *obj, const char *expr, const char *msg,
const char *file, int line, const char *function)