ui/gtk: prevent ui lock up when dpy_gl_update called again before current draw event occurs

A warning, "qemu: warning: console: no gl-unblock within" followed by
guest scanout lockup can happen if dpy_gl_update is called in a row
and the second call is made before gd_draw_event scheduled by the first
call is taking place. This is because draw call returns without decrementing
gl_block ref count if the dmabuf was already submitted as shown below.

(gd_gl_area_draw/gd_egl_draw)

        if (dmabuf) {
            if (!dmabuf->draw_submitted) {
                return;
            } else {
                dmabuf->draw_submitted = false;
            }
        }

So it should not schedule any redundant draw event in case draw_submitted is
already set in gd_egl_fluch/gd_gl_area_scanout_flush.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Vivek Kasireddy <vivek.kasireddy@intel.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20221021192315.9110-1-dongwon.kim@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/ui/gtk-gl-area.c b/ui/gtk-gl-area.c
index 682638a197..7696df1f6b 100644
--- a/ui/gtk-gl-area.c
+++ b/ui/gtk-gl-area.c
@@ -278,7 +278,7 @@ void gd_gl_area_scanout_flush(DisplayChangeListener *dcl,
 {
     VirtualConsole *vc = container_of(dcl, VirtualConsole, gfx.dcl);
 
-    if (vc->gfx.guest_fb.dmabuf) {
+    if (vc->gfx.guest_fb.dmabuf && !vc->gfx.guest_fb.dmabuf->draw_submitted) {
         graphic_hw_gl_block(vc->gfx.dcl.con, true);
         vc->gfx.guest_fb.dmabuf->draw_submitted = true;
     }