[PATCH] Xext/shm: Detach SHM segment after Pixmap is released

[Chris Wilson]

The GPU may still have a reference to the SHM segment which would only
be finally released when the Pixmap is destroy. So we can only detach
the SHM segment (and thereby making the memory unaccessible) after the
backend has had a chance to flush any remaining references.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85058
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 Xext/shm.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/Xext/shm.c b/Xext/shm.c
index 4dad8b6..b787918 100644
--- a/Xext/shm.c
+++ b/Xext/shm.c
@@ -248,21 +248,20 @@ ShmDestroyPixmap(PixmapPtr pPixmap)
 {
     ScreenPtr pScreen = pPixmap->drawable.pScreen;
     ShmScrPrivateRec *screen_priv = ShmGetScreenPriv(pScreen);
+    void *shmdesc = NULL;
     Bool ret;
 
-    if (pPixmap->refcnt == 1) {
-        ShmDescPtr shmdesc;
-
-        shmdesc = (ShmDescPtr) dixLookupPrivate(&pPixmap->devPrivates,
-                                                shmPixmapPrivateKey);
-        if (shmdesc)
-            ShmDetachSegment((void *) shmdesc, pPixmap->drawable.id);
-    }
+    if (pPixmap->refcnt == 1)
+        shmdesc = dixLookupPrivate(&pPixmap->devPrivates, shmPixmapPrivateKey);
 
     pScreen->DestroyPixmap = screen_priv->destroyPixmap;
     ret = (*pScreen->DestroyPixmap) (pPixmap);
     screen_priv->destroyPixmap = pScreen->DestroyPixmap;
     pScreen->DestroyPixmap = ShmDestroyPixmap;
+
+    if (shmdesc)
+	ShmDetachSegment(shmdesc, pPixmap->drawable.id);
+
     return ret;
 }
 
-- 
1.9.1