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gh-110481: Fix biased reference counting queue initialization. (#117271)

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The biased reference counting queue must be initialized from the bound
(active) thread because it uses `_Py_ThreadId()` as the key in a hash
table.
This commit is contained in:
Sam Gross 2024-03-28 09:28:39 -04:00 • committed by GitHub
parent 9a1e55b8c5
commit 8dbfdb2957
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2 changed files with 18 additions and 6 deletions
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14
Python/brc.c
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@ -119,6 +119,8 @@ _Py_brc_merge_refcounts(PyThreadState *tstate)
struct _brc_thread_state *brc = &((_PyThreadStateImpl *)tstate)->brc;
struct _brc_bucket *bucket = get_bucket(tstate->interp, brc->tid);
assert(brc->tid == _Py_ThreadId());
// Append all objects into a local stack. We don't want to hold the lock
// while calling destructors.
PyMutex_Lock(&bucket->mutex);
@ -142,11 +144,12 @@ void
_Py_brc_init_thread(PyThreadState *tstate)
{
struct _brc_thread_state *brc = &((_PyThreadStateImpl *)tstate)->brc;
brc->tid = _Py_ThreadId();
uintptr_t tid = _Py_ThreadId();
// Add ourself to the hashtable
struct _brc_bucket *bucket = get_bucket(tstate->interp, brc->tid);
struct _brc_bucket *bucket = get_bucket(tstate->interp, tid);
PyMutex_Lock(&bucket->mutex);
brc->tid = tid;
llist_insert_tail(&bucket->root, &brc->bucket_node);
PyMutex_Unlock(&bucket->mutex);
}
@ -155,6 +158,13 @@ void
_Py_brc_remove_thread(PyThreadState *tstate)
{
struct _brc_thread_state *brc = &((_PyThreadStateImpl *)tstate)->brc;
if (brc->tid == 0) {
// The thread state may have been created, but never bound to a native
// thread and therefore never added to the hashtable.
assert(tstate->_status.bound == 0);
return;
}
struct _brc_bucket *bucket = get_bucket(tstate->interp, brc->tid);
// We need to fully process any objects to merge before removing ourself