Remove hack that causes deadlock when waiting in eglSwapBuffers

This hack was added to work around the problem of calling
wl_display_iterate in two separate threads, but now that we are
are enforceing that wl_display_iterate can only be called in one thread
it now causes a deadlock when we are waiting in eglSwapBuffers for the
gui thread to actually call wl_display_iterate.

Change-Id: Id3153b184c191494838fc363380f7cae621ac64e
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>

src/plugins/platforms/wayland/gl_integration/wayland_egl/qwaylandglcontext.cpp

@@ -49,7 +49,6 @@
 
 #include <QtGui/QPlatformOpenGLContext>
 #include <QtGui/QSurfaceFormat>
-#include <QtCore/QMutex>
 
 QWaylandGLContext::QWaylandGLContext(EGLDisplay eglDisplay, const QSurfaceFormat &format, QPlatformOpenGLContext *share)
     : QPlatformOpenGLContext()
@@ -85,13 +84,8 @@ void QWaylandGLContext::doneCurrent()
     eglMakeCurrent(m_eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
 }
 
-// lock to sync with QWaylandDisplay event loop ( defined in qwaylanddisplay.cpp )
-extern QMutex g_waylandLock;
-
 void QWaylandGLContext::swapBuffers(QPlatformSurface *surface)
 {
-    QMutexLocker l(&g_waylandLock);
-
     EGLSurface eglSurface = static_cast<QWaylandEglWindow *>(surface)->eglSurface();
     eglSwapBuffers(m_eglDisplay, eglSurface);
 }

src/plugins/platforms/wayland/qwaylanddisplay.cpp

@@ -70,11 +70,6 @@
 #include <stdio.h>
 #include <errno.h>
 
-#include <QMutex>
-
-// lock used to syncronize swap-buffers with the display-event-loop
-QMutex g_waylandLock;
-
 #include <QtCore/QDebug>
 
 struct wl_surface *QWaylandDisplay::createSurface(void *handle)
@@ -184,32 +179,27 @@ void QWaylandDisplay::flushRequests()
 
 void QWaylandDisplay::readEvents()
 {
-    if (g_waylandLock.tryLock())
-    {
-        fd_set fds;
-        FD_ZERO(&fds);
-        FD_SET(mFd, &fds);
-
-        fd_set nds;
-        FD_ZERO(&nds);
-        fd_set rs = fds;
-        fd_set ws = nds;
-        fd_set es = nds;
-        timeval timeout;
-
-        timeout.tv_sec = 0;
-        timeout.tv_usec = 0;
-
-        int ret = ::select(mFd+1, &rs, &ws, &es, &timeout );
-
-        if (ret <= 0) {
-            g_waylandLock.unlock();
-            return;
-        }
-
-        wl_display_iterate(mDisplay, WL_DISPLAY_READABLE);
-        g_waylandLock.unlock();
+    fd_set fds;
+    FD_ZERO(&fds);
+    FD_SET(mFd, &fds);
+
+    fd_set nds;
+    FD_ZERO(&nds);
+    fd_set rs = fds;
+    fd_set ws = nds;
+    fd_set es = nds;
+    timeval timeout;
+
+    timeout.tv_sec = 0;
+    timeout.tv_usec = 0;
+
+    int ret = ::select(mFd+1, &rs, &ws, &es, &timeout );
+
+    if (ret <= 0) {
+        return;
     }
+
+    wl_display_iterate(mDisplay, WL_DISPLAY_READABLE);
 }
 
 void QWaylandDisplay::blockingReadEvents()