Data race in QPointer (QtSharedPointer::ExternalRefCountData::getAndRef)

WARNING: ThreadSanitizer: data race (pid=391944)
  Atomic write of size 4 at 0x72040062aba0 by thread T103:
    #0 std::__atomic_base<int>::fetch_add(int, std::memory_order) /usr/include/c++/14/bits/atomic_base.h:631 (libQt6Core_tsan.so.6+0xf1f24)
    #1 bool QAtomicOps<int>::ref<int>(std::atomic<int>&) qtbase/src/corelib/thread/qatomic_cxx11.h:259 (libQt6Core_tsan.so.6+0xf1f24)
    #2 QBasicAtomicInteger<int>::ref() qtbase/src/corelib/thread/qbasicatomic.h:47 (libQt6Core_tsan.so.6+0xef5f6)
    #3 QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) qtbase/src/corelib/tools/qsharedpointer.cpp:1536 (libQt6Core_tsan.so.6+0x5f5cf2)
    #4 QWeakPointer<QObject>::QWeakPointer<QObject, true>(QObject*, bool) inst-tsan/include/QtCore/qsharedpointer_impl.h:773
    #5 QWeakPointer<QObject>& QWeakPointer<QObject>::assign<QObject>(QObject*) inst-tsan/include/QtCore/qsharedpointer_impl.h:768

  Previous write of size 8 at 0x72040062aba0 by thread T164:
    #0 operator new(unsigned long) <null> (libtsan.so.2+0xa75e1)
    #1 QtSharedPointer::ExternalRefCountData::getAndRef(QObject const*) qtbase/src/corelib/tools/qsharedpointer.cpp:1541 (libQt6Core_tsan.so.6+0x5f5d13)
    #2 QWeakPointer<QObject>::QWeakPointer<QObject, true>(QObject*, bool) inst-tsan/include/QtCore/qsharedpointer_impl.h:773
    #3 QWeakPointer<QObject>& QWeakPointer<QObject>::assign<QObject>(QObject*) inst-tsan/include/QtCore/qsharedpointer_impl.h:768

1528│ QtSharedPointer::ExternalRefCountData *QtSharedPointer::ExternalRefCountData::getAndRef(const QObject *obj)
1529│ {
1530│     Q_ASSERT(obj);
1531│     QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
1532│     Q_ASSERT_X(!d->wasDeleted, "QWeakPointer", "Detected QWeakPointer creation in a QObject being deleted");
1533│
1534│     ExternalRefCountData *that = d->sharedRefcount.loadRelaxed();
1535│     if (that) {
1536├───────> that->weakref.ref();
1537│         return that;
1538│     }
1539│
1540│     // we can create the refcount data because it doesn't exist
1541│     ExternalRefCountData *x = ::new ExternalRefCountData(Qt::Uninitialized);
1542│     x->strongref.storeRelaxed(-1);
1543│     x->weakref.storeRelaxed(2);  // the QWeakPointer that called us plus the QObject itself
1544│
1545│     ExternalRefCountData *ret;
1546│     if (d->sharedRefcount.testAndSetOrdered(nullptr, x, ret)) {     // ought to be release+acquire; this is acq_rel+acquire
1547│         ret = x;
1548│     } else {
1549│         // ~ExternalRefCountData has a Q_ASSERT, so we use this trick to
1550│         // only execute this if Q_ASSERTs are enabled
1551│         Q_ASSERT((x->weakref.storeRelaxed(0), true));
1552│         ::delete x;
1553│         ret->weakref.ref();
1554│     }
1555│     return ret;
1556│ }