2 files changed, 32 insertions, 29 deletions

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index cecdbda92..7c8ecadaa 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -610,29 +610,34 @@ const wl_callback_listener QWaylandWindow::callbackListener = {
         Q_UNUSED(callback);
         Q_UNUSED(time);
         auto *window = static_cast<QWaylandWindow*>(data);
-        if (window->thread() != QThread::currentThread())
-            QMetaObject::invokeMethod(window, [=] { window->handleFrameCallback(); }, Qt::QueuedConnection);
-        else
-            window->handleFrameCallback();
+        window->handleFrameCallback();
     }
 };
 
 void QWaylandWindow::handleFrameCallback()
 {
-    bool wasExposed = isExposed();
+    // Stop the timer and stop waiting immediately
+    int timerId = mFrameCallbackTimerId.fetchAndStoreOrdered(-1);
+    mWaitingForFrameCallback = false;
 
-    if (mFrameCallbackTimerId != -1) {
-        killTimer(mFrameCallbackTimerId);
-        mFrameCallbackTimerId = -1;
-    }
+    // The rest can wait until we can run it on the correct thread
+    auto doHandleExpose = [this, timerId]() {
+        if (timerId != -1)
+            killTimer(timerId);
 
-    mWaitingForFrameCallback = false;
-    mFrameCallbackTimedOut = false;
+        bool wasExposed = isExposed();
+        mFrameCallbackTimedOut = false;
+        if (!wasExposed && isExposed()) // Did setting mFrameCallbackTimedOut make the window exposed?
+            sendExposeEvent(QRect(QPoint(), geometry().size()));
+        if (wasExposed && hasPendingUpdateRequest())
+            deliverUpdateRequest();
+    };
 
-    if (!wasExposed && isExposed())
-        sendExposeEvent(QRect(QPoint(), geometry().size()));
-    if (wasExposed && hasPendingUpdateRequest())
-        deliverUpdateRequest();
+    if (thread() != QThread::currentThread()) {
+        QMetaObject::invokeMethod(this, doHandleExpose);
+    } else {
+        doHandleExpose();
+    }
 }
 
 QMutex QWaylandWindow::mFrameSyncMutex;
@@ -654,11 +659,11 @@ bool QWaylandWindow::waitForFrameSync(int timeout)
     }
 
     // Stop current frame timer if any, can't use killTimer directly, because we might be on a diffent thread
-    if (mFrameCallbackTimerId != -1) {
-        int id = mFrameCallbackTimerId;
-        mFrameCallbackTimerId = -1;
-        QMetaObject::invokeMethod(this, [=] { killTimer(id); }, Qt::QueuedConnection);
-    }
+    // Ordered semantics is needed to avoid stopping the timer twice and not miss it when it's
+    // started by other writes
+    int fcbId = mFrameCallbackTimerId.fetchAndStoreOrdered(-1);
+    if (fcbId != -1)
+        QMetaObject::invokeMethod(this, [=] { killTimer(fcbId); }, Qt::QueuedConnection);
 
     return !mWaitingForFrameCallback;
 }
@@ -1090,9 +1095,9 @@ void QWaylandWindow::timerEvent(QTimerEvent *event)
         }
     }
 
-    if (event->timerId() == mFrameCallbackTimerId) {
-        killTimer(mFrameCallbackTimerId);
-        mFrameCallbackTimerId = -1;
+
+    if (mFrameCallbackTimerId.testAndSetOrdered(event->timerId(), -1)) {
+        killTimer(event->timerId());
         qCDebug(lcWaylandBackingstore) << "Didn't receive frame callback in time, window should now be inexposed";
         mFrameCallbackTimedOut = true;
         mWaitingForUpdate = false;
@@ -1154,11 +1159,9 @@ void QWaylandWindow::handleUpdate()
     mWaitingForUpdate = false;
 
     // Stop current frame timer if any, can't use killTimer directly, see comment above.
-    if (mFrameCallbackTimerId != -1) {
-        int id = mFrameCallbackTimerId;
-        mFrameCallbackTimerId = -1;
-        QMetaObject::invokeMethod(this, [=] { killTimer(id); }, Qt::QueuedConnection);
-    }
+    int fcbId = mFrameCallbackTimerId.fetchAndStoreOrdered(-1);
+    if (fcbId != -1)
+        QMetaObject::invokeMethod(this, [=] { killTimer(fcbId); }, Qt::QueuedConnection);
 
     // Start a timer for handling the case when the compositor stops sending frame callbacks.
     QMetaObject::invokeMethod(this, [=] { // Again; can't do it directly
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index c47123dc9..e8c9d5684 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -216,7 +216,7 @@ protected:
     WId mWindowId;
     bool mWaitingForFrameCallback = false;
     bool mFrameCallbackTimedOut = false; // Whether the frame callback has timed out
-    int mFrameCallbackTimerId = -1; // Started on commit, reset on frame callback
+    QAtomicInt mFrameCallbackTimerId = -1; // Started on commit, reset on frame callback
     struct ::wl_callback *mFrameCallback = nullptr;
     struct ::wl_event_queue *mFrameQueue = nullptr;
     QWaitCondition mFrameSyncWait;