[RFC][PATCH xserver] Multi-buffered flips on subsurfaces seg fault in Mesa

[Adam Jackson]

On Mon, 2018-01-29 at 17:54 +0100, Roman Gilg wrote:
> The above patch series only allows flips on a child window with the same
> dimensions as its parent xwl_window. For flips on child windows (for example
> the video view port of a video player in windowed mode, see here:
> http://www.subdiff.de/assets/images/2017-07-28-a-new-beginning.jpg) I wanted
> to use Wayland subsurfaces as in the attached patch.
> 
> The flipping itself works well on Weston and on KWin. But when shutting down
> KWin in the end I get always a segmentation fault in Mesa when cleaning up EGL
> via eglTerminate(EGLDisplay) through libepoxy.
> 
> I pinpointed the seg fault to be a missing destroyImage function pointer here:
> https://cgit.freedesktop.org/mesa/mesa/tree/src/egl/drivers/dri2/egl_dri2.c#n2685

Pretty sure that can't be the problem. Every DRI driver implements that
function, as far as I can tell. Possibly what's really happening is by
the time you get to that crash the dri2_egl_display has already been
torn down, ie that dri2_dpy is NULL, not the destroyImage hook.

- ajax