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gh-130794: Process interpreter QSBR queue in _PyMem_AbandonDelayed. (gh-130808)

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This avoids a case where the interpreter's queue of memory to be freed
could grow rapidly if there are many short lived threads.
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Sam Gross 2025-03-04 18:04:04 -05:00 • committed by GitHub
parent cb67b44ca9
commit 2f6e0e9f70
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3 changed files with 25 additions and 9 deletions
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2
Misc/NEWS.d/next/Core_and_Builtins/2025-03-03-20-33-44.gh-issue-130794.LwtGQc.rst Normal file
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@ -0,0 +1,2 @@
Fix memory leak in the :term:`free threaded <free threading>` build when
resizing a shared list or dictionary from multiple short-lived threads.

31
Objects/obmalloc.c
View file

@ -1303,6 +1303,18 @@ static void
process_interp_queue(struct _Py_mem_interp_free_queue *queue,
struct _qsbr_thread_state *qsbr, delayed_dealloc_cb cb,
void *state)
{
assert(PyMutex_IsLocked(&queue->mutex));
process_queue(&queue->head, qsbr, false, cb, state);
int more_work = !llist_empty(&queue->head);
_Py_atomic_store_int_relaxed(&queue->has_work, more_work);
}
static void
maybe_process_interp_queue(struct _Py_mem_interp_free_queue *queue,
struct _qsbr_thread_state *qsbr, delayed_dealloc_cb cb,
void *state)
{
if (!_Py_atomic_load_int_relaxed(&queue->has_work)) {
return;
@ -1310,11 +1322,7 @@ process_interp_queue(struct _Py_mem_interp_free_queue *queue,
// Try to acquire the lock, but don't block if it's already held.
if (_PyMutex_LockTimed(&queue->mutex, 0, 0) == PY_LOCK_ACQUIRED) {
process_queue(&queue->head, qsbr, false, cb, state);
int more_work = !llist_empty(&queue->head);
_Py_atomic_store_int_relaxed(&queue->has_work, more_work);
process_interp_queue(queue, qsbr, cb, state);
PyMutex_Unlock(&queue->mutex);
}
}
@ -1329,7 +1337,7 @@ _PyMem_ProcessDelayed(PyThreadState *tstate)
process_queue(&tstate_impl->mem_free_queue, tstate_impl->qsbr, true, NULL, NULL);
// Process shared interpreter work
process_interp_queue(&interp->mem_free_queue, tstate_impl->qsbr, NULL, NULL);
maybe_process_interp_queue(&interp->mem_free_queue, tstate_impl->qsbr, NULL, NULL);
}
void
@ -1342,7 +1350,7 @@ _PyMem_ProcessDelayedNoDealloc(PyThreadState *tstate, delayed_dealloc_cb cb, voi
process_queue(&tstate_impl->mem_free_queue, tstate_impl->qsbr, true, cb, state);
// Process shared interpreter work
process_interp_queue(&interp->mem_free_queue, tstate_impl->qsbr, cb, state);
maybe_process_interp_queue(&interp->mem_free_queue, tstate_impl->qsbr, cb, state);
}
void
@ -1364,10 +1372,15 @@ _PyMem_AbandonDelayed(PyThreadState *tstate)
return;
}
// Merge the thread's work queue into the interpreter's work queue.
PyMutex_Lock(&interp->mem_free_queue.mutex);
// Merge the thread's work queue into the interpreter's work queue.
llist_concat(&interp->mem_free_queue.head, queue);
_Py_atomic_store_int_relaxed(&interp->mem_free_queue.has_work, 1);
// Process the merged queue now (see gh-130794).
_PyThreadStateImpl *this_tstate = (_PyThreadStateImpl *)_PyThreadState_GET();
process_interp_queue(&interp->mem_free_queue, this_tstate->qsbr, NULL, NULL);
PyMutex_Unlock(&interp->mem_free_queue.mutex);
assert(llist_empty(queue)); // the thread's queue is now empty

1
Python/qsbr.c
View file

@ -161,6 +161,7 @@ bool
_Py_qsbr_poll(struct _qsbr_thread_state *qsbr, uint64_t goal)
{
assert(_Py_atomic_load_int_relaxed(&_PyThreadState_GET()->state) == _Py_THREAD_ATTACHED);
assert(((_PyThreadStateImpl *)_PyThreadState_GET())->qsbr == qsbr);
if (_Py_qbsr_goal_reached(qsbr, goal)) {
return true;