QObjectData: relax accesses to postedEvents

If one wants to access the event list itself, they have to lock the
postedEventList mutex, so none of these probably need any more ordering
than Relaxed. I've left most of them in Acquire/Release because we don't
have time to reason whether Relaxed suffices (the one exception is a
loadRelaxed() that calls a function that does loadAcquire()).

Amends commit ba6c1d2.

Pick-to: 6.8
Change-Id: I35810f961b96aaf63d74fffd1eda73b3e059583d
Reviewed-by: Fabian Kosmale <[email protected]>

src/corelib/kernel/qcoreapplication.cpp

@@ -503,7 +503,7 @@ void QCoreApplicationPrivate::cleanupThreadData()
         const auto locker = qt_scoped_lock(thisThreadData->postEventList.mutex);
         for (const QPostEvent &pe : std::as_const(thisThreadData->postEventList)) {
             if (pe.event) {
-                --pe.receiver->d_func()->postedEvents;
+                pe.receiver->d_func()->postedEvents.fetchAndSubAcquire(1);
                 pe.event->m_posted = false;
                 delete pe.event;
             }
@@ -1660,7 +1660,7 @@ void QCoreApplication::postEvent(QObject *receiver, QEvent *event, int priority)
     QThreadData *data = locker.threadData;
 
     // if this is one of the compressible events, do compression
-    if (receiver->d_func()->postedEvents
+    if (receiver->d_func()->postedEvents.loadAcquire()
         && self && self->compressEvent(event, receiver, &data->postEventList)) {
         Q_TRACE(QCoreApplication_postEvent_event_compressed, receiver, event);
         return;
@@ -1673,7 +1673,7 @@ void QCoreApplication::postEvent(QObject *receiver, QEvent *event, int priority)
     data->postEventList.addEvent(QPostEvent(receiver, event, priority));
     Q_UNUSED(eventDeleter.release());
     event->m_posted = true;
-    ++receiver->d_func()->postedEvents;
+    receiver->d_func()->postedEvents.fetchAndAddRelease(1);
     data->canWait = false;
     locker.unlock();
 
@@ -1774,7 +1774,8 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
     // events, canWait will be set to false.
     data->canWait = (data->postEventList.size() == 0);
 
-    if (data->postEventList.size() == 0 || (receiver && !receiver->d_func()->postedEvents)) {
+    if (data->postEventList.size() == 0
+            || (receiver && !receiver->d_func()->postedEvents.loadAcquire())) {
         --data->postEventList.recursion;
         return;
     }
@@ -1903,7 +1904,7 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
         QEvent *e = pe.event;
         QObject * r = pe.receiver;
 
-        --r->d_func()->postedEvents;
+        r->d_func()->postedEvents.fetchAndSubAcquire(1);
         Q_ASSERT(r->d_func()->postedEvents >= 0);
 
         // next, update the data structure so that we're ready
@@ -1954,7 +1955,7 @@ void QCoreApplication::removePostedEvents(QObject *receiver, int eventType)
     // happen while the event loop is in the middle of posting events,
     // and when we get here, we may not have any more posted events
     // for this object.
-    if (receiver && !receiver->d_func()->postedEvents)
+    if (receiver && !receiver->d_func()->postedEvents.loadAcquire())
         return;
 
     //we will collect all the posted events for the QObject
@@ -1968,7 +1969,7 @@ void QCoreApplication::removePostedEvents(QObject *receiver, int eventType)
 
         if ((!receiver || pe.receiver == receiver)
             && (pe.event && (eventType == 0 || pe.event->type() == eventType))) {
-            --pe.receiver->d_func()->postedEvents;
+            pe.receiver->d_func()->postedEvents.fetchAndSubAcquire(1);
             pe.event->m_posted = false;
             events.append(pe.event);
             const_cast<QPostEvent &>(pe).event = nullptr;
@@ -2029,7 +2030,7 @@ void QCoreApplicationPrivate::removePostedEvent(QEvent * event)
                      pe.receiver->metaObject()->className(),
                      pe.receiver->objectName().toLocal8Bit().data());
 #endif
-            --pe.receiver->d_func()->postedEvents;
+            pe.receiver->d_func()->postedEvents.fetchAndSubAcquire(1);
             pe.event->m_posted = false;
             delete pe.event;
             const_cast<QPostEvent &>(pe).event = nullptr;

src/corelib/kernel/qobject.cpp

@@ -172,7 +172,7 @@ QObjectPrivate::QObjectPrivate(int version)
     isDeletingChildren = false;                 // set by deleteChildren()
     sendChildEvents = true;                     // if we should send ChildAdded and ChildRemoved events to parent
     receiveChildEvents = true;
-    postedEvents = 0;
+    postedEvents.storeRelaxed(0);
     extraData = nullptr;
     metaObject = nullptr;
     isWindow = false;
@@ -200,7 +200,7 @@ QObjectPrivate::~QObjectPrivate()
         }
     }
 
-    if (postedEvents)
+    if (postedEvents.loadRelaxed())
         QCoreApplication::removePostedEvents(q_ptr, 0);
 
     thisThreadData->deref();

src/corelib/thread/qthread.cpp

@@ -68,7 +68,7 @@ QThreadData::~QThreadData()
     for (qsizetype i = 0; i < postEventList.size(); ++i) {
         const QPostEvent &pe = postEventList.at(i);
         if (pe.event) {
-            --pe.receiver->d_func()->postedEvents;
+            pe.receiver->d_func()->postedEvents.fetchAndSubRelaxed(1);
             pe.event->m_posted = false;
             delete pe.event;
         }