[PATCH 6/7] Present: Check for window/fence destroyed when idling pixmaps

[Keith Packard]

A client destroying objects in the middle of an unflip can end up
having the screen flip window or fence set to NULL in the unflip
notify path. Check for these and don't try to use those objects.

Signed-off-by: Keith Packard <keithp at keithp.com>
---
 present/present.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/present/present.c b/present/present.c
index 4c97ce4..fab105d 100644
--- a/present/present.c
+++ b/present/present.c
@@ -184,8 +184,10 @@ present_vblank_notify(present_vblank_ptr vblank, CARD8 kind, CARD8 mode, uint64_
 static void
 present_pixmap_idle(PixmapPtr pixmap, WindowPtr window, CARD32 serial, struct present_fence *present_fence)
 {
-    present_fence_set_triggered(present_fence);
-    present_send_idle_notify(window, serial, pixmap, present_fence);
+    if (present_fence)
+        present_fence_set_triggered(present_fence);
+    if (window)
+        present_send_idle_notify(window, serial, pixmap, present_fence);
 }
 
 RRCrtcPtr
@@ -297,7 +299,8 @@ present_flip_idle(ScreenPtr screen)
     if (screen_priv->flip_pixmap) {
         present_pixmap_idle(screen_priv->flip_pixmap, screen_priv->flip_window,
                             screen_priv->flip_serial, screen_priv->flip_idle_fence);
-        present_fence_destroy(screen_priv->flip_idle_fence);
+        if (screen_priv->flip_idle_fence)
+            present_fence_destroy(screen_priv->flip_idle_fence);
         dixDestroyPixmap(screen_priv->flip_pixmap, screen_priv->flip_pixmap->drawable.id);
         screen_priv->flip_crtc = NULL;
         screen_priv->flip_window = NULL;
-- 
1.8.4.2