Re: mesa garbage collection - pardon the silly questions...

On Fri, 18 May 2007, leon zadorin wrote:

> I am in a process of investigating some strange app's behaviour, where 
> having
> 1) opened display connecton
> 2) initialised glx
> 3) attached window to glx and made the glx context current, etc.
> 4) then de-initialised glx, destroyed window, closed display
> connecton, etc. etc.
> 5) then opened display connection again
> 6) then trying to initialise glx crashes (at glx creating a context)
> on NetBSD-current/macppc port...

> I have traced the crash to XSync call in mesa garbage colleciton...
> anyway... in a process of my learning (so pardon if my questions ar
> rather silly) the whole X thing :-) I have a question about the
> following code in:

> xc/extras/Mesa/src/mesa/drivers/x11/xm_api.c
> or 
> http://cvsweb.xfree86.org/cvsweb/xc/extras/Mesa/src/mesa/drivers/x11/xm_api.c?rev=HEAD&content-type=text/vnd.viewcvs-markup

> void XMesaGarbageCollect( void )
> {
>  XMesaBuffer b, next;
>  for (b=XMesaBufferList; b; b=next) {
>     next = b->Next;
>     if (b->display && b->frontbuffer && b->type == WINDOW) {
> #ifdef XFree86Server
> 	 /* NOT_NEEDED */
> #else
>        XSync(b->display, False);
>        if (!window_exists( b->display, b->frontbuffer )) {
>           /* found a dead window, free the ancillary info */
>           XMesaDestroyBuffer( b );
>        }
> #endif
>     }
>  }
> }

> The above code checks for vaild (non-null) "display" and "frontbuffer"
> before calling Xsync... but how does it know that "b->display" is
> still in the open state (i.e. that XCloseDisplay was not called on
> "b->display")... or is it guaranteed by some other code that
> XMesaBufferList will only have open displays... or is it OK to call
> XSync on a closed display?

All my build logs show that xm_api.c is always compiled with 
-DXFree86Server, making XMesaGarbageCollect() a no-op.  So it would seem 
that the way this is built on NetBSD is incorrect.

Marc.

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