[PATCH xserver] present: Only call restore_screen_pixmap once from set_abort_flip

[Michel Dänzer]

From: Michel Dänzer <michel.daenzer at amd.com>

present_restore_screen_pixmap's work doesn't need to be done several
times for the same pending flip.

Fixes a crash if the X server quits while a flip is pending, in which
case present_set_abort_flip may be called several times, including when
screen->root is already cleared to NULL.

Signed-off-by: Michel Dänzer <michel.daenzer at amd.com>
---
 present/present.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/present/present.c b/present/present.c
index 5210832..5fde846 100644
--- a/present/present.c
+++ b/present/present.c
@@ -455,9 +455,10 @@ present_set_abort_flip(ScreenPtr screen)
 {
     present_screen_priv_ptr screen_priv = present_screen_priv(screen);
 
-    present_restore_screen_pixmap(screen);
-
-    screen_priv->flip_pending->abort_flip = TRUE;
+    if (!screen_priv->flip_pending->abort_flip) {
+        present_restore_screen_pixmap(screen);
+        screen_priv->flip_pending->abort_flip = TRUE;
+    }
 }
 
 static void
-- 
2.8.1