QProperty: fix threading issues

QObject's cache the binding status pointer to avoid TLS lookups.
However, when an object is moved to a different thread, we need to
update the cached pointer (as the original thread might stop and thus no
longer exist, and to correctly allow setting up bindings in the object's
thread).
Fix this by also storing the binding status in QThreadPrivate and
updating the object's binding status when moved. This does only work
when the thread is already running, though. If it is not running, we
instead treat the QThreadPrivate's status pointer as a pointer to a
vector of pending objects. Once the QThread has been started, we check
if there are pending objects, and update them at this point.

Pick-to: 6.2 6.3
Fixes: QTBUG-101177
Change-Id: I0490bbbdc1a17cb5f85044ad6eb2e1a8c759d4b7
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/corelib/thread/qthread.cpp b/src/corelib/thread/qthread.cpp
index 4cfcab2258..994d77926c 100644
--- a/src/corelib/thread/qthread.cpp
+++ b/src/corelib/thread/qthread.cpp
@@ -43,6 +43,7 @@
 #include "qmutex.h"
 #include "qreadwritelock.h"
 #include "qabstracteventdispatcher.h"
+#include "qbindingstorage.h"
 
 #include <qeventloop.h>
 
@@ -195,6 +196,7 @@ QThreadPrivate::QThreadPrivate(QThreadData *d)
 
 QThreadPrivate::~QThreadPrivate()
 {
+    delete pendingObjectsWithBindingStatusChange();
     data->deref();
 }
 
@@ -552,6 +554,13 @@ uint QThread::stackSize() const
 int QThread::exec()
 {
     Q_D(QThread);
+    const auto status = QtPrivate::getBindingStatus(QtPrivate::QBindingStatusAccessToken{});
+    if (auto pendingObjects = d->pendingObjectsWithBindingStatusChange()) {
+        for (auto obj: *pendingObjects)
+            QObjectPrivate::get(obj)->reinitBindingStorageAfterThreadMove();
+        delete pendingObjects;
+    }
+    d->m_statusOrPendingObjects.storeRelease(quintptr(status));
     QMutexLocker locker(&d->mutex);
     d->data->quitNow = false;
     if (d->exited) {
@@ -953,6 +962,7 @@ QThreadPrivate::QThreadPrivate(QThreadData *d) : data(d ? d : new QThreadData)
 
 QThreadPrivate::~QThreadPrivate()
 {
+    delete pendingObjectsWithBindingStatusChange();
     data->thread.storeRelease(nullptr); // prevent QThreadData from deleting the QThreadPrivate (again).
     delete data;
 }