Unichrome DRI:

Fixed an apparent race condition during locking and drawable info updating,
the result of which was the DRI client leaving traces on the screen rendering
where the drawable previously had been.
If the driver hangs X for a second or so and then restarts, this is probably
the place to look. (Thomas Hellstr?m)

src/mesa/drivers/dri/unichrome/via_context.c

@@ -986,15 +986,7 @@ void viaGetLock(viaContextPtr vmesa, GLuint flags)
 #endif
     drmGetLock(vmesa->driFd, vmesa->hHWContext, flags);
 
-    do {
-	    DRM_UNLOCK(psp->fd, &psp->pSAREA->lock,
-		   pdp->driContextPriv->hHWContext);
-	    DRM_SPINLOCK(&psp->pSAREA->drawable_lock, psp->drawLockID);
-            __driUtilUpdateDrawableInfo(dPriv);
-	    DRM_SPINUNLOCK(&psp->pSAREA->drawable_lock, psp->drawLockID);
-	    DRM_LIGHT_LOCK(psp->fd, &psp->pSAREA->lock,
-	    	       pdp->driContextPriv->hHWContext);
-    } while (0);
+    DRI_VALIDATE_DRAWABLE_INFO( sPriv, dPriv );
 
     if (sarea->ctxOwner != me) {
         vmesa->uploadCliprects = GL_TRUE;