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

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merged 2 commits into from
Mar 28, 2024
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gh-110481: Fix biased reference counting queue initialization. #117271

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e697b37
gh-110481: Fix biased reference counting queue initialization.
colesbury Mar 26, 2024
87f390c
Fix `_Py_brc_remove_thread()`.
colesbury Mar 27, 2024
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14 changes: 12 additions & 2 deletions Python/brc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand All @@ -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);
}
Expand All @@ -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
Expand Down
10 changes: 6 additions & 4 deletions Python/pystate.c
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Expand Up @@ -261,6 +261,12 @@ bind_tstate(PyThreadState *tstate)
tstate->native_thread_id = PyThread_get_thread_native_id();
#endif

#ifdef Py_GIL_DISABLED
// Initialize biased reference counting inter-thread queue. Note that this
// needs to be initialized from the active thread.
_Py_brc_init_thread(tstate);
#endif

// mimalloc state needs to be initialized from the active thread.
tstate_mimalloc_bind(tstate);

Expand Down Expand Up @@ -1412,10 +1418,6 @@ init_threadstate(_PyThreadStateImpl *_tstate,
tstate->what_event = -1;
tstate->previous_executor = NULL;

#ifdef Py_GIL_DISABLED
// Initialize biased reference counting inter-thread queue
_Py_brc_init_thread(tstate);
#endif
llist_init(&_tstate->mem_free_queue);

if (interp->stoptheworld.requested || _PyRuntime.stoptheworld.requested) {
Expand Down
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