[PATCH weston] simple-egl: Avoid race condition.

[Kristian Høgsberg]

On Fri, Aug 31, 2012 at 03:18:15AM -0600, Scott Moreau wrote:
> After explaining the problem on irc, Pekka dictated this solution which works.
> The problem is that simple-egl can hang when toggling fullscreen because of a
> race where (quoting Pekka) "if it dispatches the frame callback simple-egl
> itself requested before the Mesa's own frame callback came, simple-egl will go
> to its redraw routing and call eglSwapBuffers so you end up effectively calling
> eglSwapBuffers from within eglSwapBuffers, and deadlock". This patch avoids
> redrawing (which calls eglSwapBuffers) when there is a pending frame callback.

Right, sure.  We really need to fix the eglSwapBuffer problem though,
it's been there for way too long.

Kristian

> ---
>  clients/simple-egl.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/clients/simple-egl.c b/clients/simple-egl.c
> index c52c82c..de93e09 100644
> --- a/clients/simple-egl.c
> +++ b/clients/simple-egl.c
> @@ -264,7 +264,9 @@ configure_callback(void *data, struct wl_callback *callback, uint32_t  time)
>  	wl_callback_destroy(callback);
>  
>  	window->configured = 1;
> -	redraw(data, NULL, time);
> +
> +	if (window->callback == NULL)
> +		redraw(data, NULL, time);
>  }
>  
>  static struct wl_callback_listener configure_callback_listener = {
> @@ -363,6 +365,9 @@ redraw(void *data, struct wl_callback *callback, uint32_t time)
>  	static uint32_t start_time = 0;
>  	struct wl_region *region;
>  
> +	assert(window->callback == callback);
> +	window->callback = NULL;
> +
>  	if (callback)
>  		wl_callback_destroy(callback);
>  
> -- 
> 1.7.11.4
> 
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