[libvirt] [PULL 5/7] vnc: fix update stalls

[Gerd Hoffmann]

vnc aborts display update jobs on video mode switches and page flips.
That can cause vnc update stalls in case an unfinished vnc job gets
aborted.  The vnc client will never receive the requested update then.
Fix that by copying the state from job_update back to update in that
case.

Reports complain about stalls with two or more clients being connected
at the same time, on some but not all connections.  I suspect it can
also happen with a single connection, multiple connections only make
this more much likely to happen.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1662260
Reported-by: Ying Fang <fangying1 at huawei.com>
Signed-off-by: Gerd Hoffmann <kraxel at redhat.com>
Reviewed-by: Ying Fang <fangying1 at huawei.com>
Message-id: 20190305130930.24516-1-kraxel at redhat.com
---
 ui/vnc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/ui/vnc.c b/ui/vnc.c
index da4a21d4ce94..2f2ab62fcf71 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -700,6 +700,12 @@ static void vnc_abort_display_jobs(VncDisplay *vd)
     }
     QTAILQ_FOREACH(vs, &vd->clients, next) {
         vnc_lock_output(vs);
+        if (vs->update == VNC_STATE_UPDATE_NONE &&
+            vs->job_update != VNC_STATE_UPDATE_NONE) {
+            /* job aborted before completion */
+            vs->update = vs->job_update;
+            vs->job_update = VNC_STATE_UPDATE_NONE;
+        }
         vs->abort = false;
         vnc_unlock_output(vs);
     }
-- 
2.18.1