From 71a854f4eced28282df72e1b25888929799e8ee7 Mon Sep 17 00:00:00 2001
From: David Edmundson <davidedmundson@kde.org>
Date: Sun, 23 Jun 2019 14:48:30 +0200
Subject: [PATCH 4/5] Client: Make handleUpdate aware of exposure changes

The wl_surface can be destroyed whilst a render is happening. Calling
wl_surface::frame after the window is reset can crash as wl_surface is
null.

Change-Id: I139a9b234cb6acba81d6c1d5fa58629904a25053
---
 src/client/qwaylandwindow.cpp | 8 ++++++++
 src/client/qwaylandwindow_p.h | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/src/client/qwaylandwindow.cpp b/src/client/qwaylandwindow.cpp
index 76975b27..c6723aa7 100644
--- a/src/client/qwaylandwindow.cpp
+++ b/src/client/qwaylandwindow.cpp
@@ -72,6 +72,8 @@ Q_LOGGING_CATEGORY(lcWaylandBackingstore, "qt.qpa.wayland.backingstore")
 
 QWaylandWindow *QWaylandWindow::mMouseGrab = nullptr;
 
+QReadWriteLock mSurfaceLock;
+
 QWaylandWindow::QWaylandWindow(QWindow *window)
     : QPlatformWindow(window)
     , mDisplay(waylandScreen()->display())
@@ -197,6 +199,7 @@ void QWaylandWindow::initWindow()
 
 void QWaylandWindow::initializeWlSurface()
 {
+    QWriteLocker lock(&mSurfaceLock);
     init(mDisplay->createSurface(static_cast<QtWayland::wl_surface *>(this)));
 }
 
@@ -230,6 +233,7 @@ void QWaylandWindow::reset()
     mSubSurfaceWindow = nullptr;
     if (isInitialized()) {
         emit wlSurfaceDestroyed();
+        QWriteLocker lock(&mSurfaceLock);
         destroy();
     }
     mScreens.clear();
@@ -1142,6 +1146,10 @@ void QWaylandWindow::requestUpdate()
 void QWaylandWindow::handleUpdate()
 {
     // TODO: Should sync subsurfaces avoid requesting frame callbacks?
+    QReadLocker lock(&mSurfaceLock);
+    if (!isInitialized()) {
+        return;
+    }
 
     if (mFrameCallback) {
         wl_callback_destroy(mFrameCallback);
diff --git a/src/client/qwaylandwindow_p.h b/src/client/qwaylandwindow_p.h
index fe24224f..97884ba4 100644
--- a/src/client/qwaylandwindow_p.h
+++ b/src/client/qwaylandwindow_p.h
@@ -53,6 +53,8 @@
 
 #include <QtCore/QWaitCondition>
 #include <QtCore/QMutex>
+#include <QtCore/QReadWriteLock>
+
 #include <QtGui/QIcon>
 #include <QtCore/QVariant>
 #include <QtCore/QLoggingCategory>
@@ -277,6 +279,8 @@ private:
     static QMutex mFrameSyncMutex;
     static QWaylandWindow *mMouseGrab;
 
+    QReadWriteLock mSurfaceLock;
+
     friend class QWaylandSubSurface;
 };
 
-- 
2.22.0