On Wed,  5 Aug 2015 16:00:57 +0900
Nobuhiko Tanibata <[email protected]> wrote:

> The final list of surfaces of set render order shall be applied. So link
> of surfaces and list of surfaces in a layer shall be initialized. And
> then the order of surfaces shall be restructured.
> 
> Signed-off-by: Nobuhiko Tanibata <[email protected]>
> ---
>  ivi-shell/ivi-layout.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/ivi-shell/ivi-layout.c b/ivi-shell/ivi-layout.c
> index bb175b0..2b61ff2 100644
> --- a/ivi-shell/ivi-layout.c
> +++ b/ivi-shell/ivi-layout.c
> @@ -2082,14 +2082,14 @@ ivi_layout_layer_set_render_order(struct 
> ivi_layout_layer *ivilayer,
>               return IVI_FAILED;
>       }
>  
> -     if (pSurface == NULL) {
> -             wl_list_for_each_safe(ivisurf, next, 
> &ivilayer->pending.surface_list, pending.link) {
> -                     if (!wl_list_empty(&ivisurf->pending.link)) {
> -                             wl_list_remove(&ivisurf->pending.link);
> -                     }
> +     wl_list_for_each_safe(ivisurf, next,
> +                           &ivilayer->pending.surface_list, pending.link) {
> +             wl_list_init(&ivisurf->pending.link);
> +     }
>  
> -                     wl_list_init(&ivisurf->pending.link);
> -             }
> +     wl_list_init(&ivilayer->pending.surface_list);

Hi,

heh, I don't recall seeing this code pattern before. It looks fragile
or even dangerous, because it is init'ing a link that is part of a
list, and doing that while traversing that list. However, I think it is
safe in this case, because:

- wl_list_for_each_safe protects against removal of the current item by
  fetching the pointer to the next item before-hand, so init'ing rather
  than removing the current item is still ok, and

- the whole list is always processed through, and finally the list head
  is init'd, so all involved pointers are reset.

I've been using another pattern, e.g. src/rpi-renderer.c:1768

        while (!wl_list_empty(&output->view_cleanup_list)) {
                view = container_of(output->view_cleanup_list.next,
                                    struct rpir_view, link);
                rpir_view_destroy(view);
        }

I'm not sure if we should prefer one or the other, because I'm
obviously biased in my judgement. :-)

The latter one does not involve temporarily broken list structures...

> +
> +     if (pSurface == NULL || number ==0) {
>               ivilayer->event_mask |= IVI_NOTIFICATION_REMOVE;
>               return IVI_SUCCEEDED;
>       }

Reviewed-by: Pekka Paalanen <[email protected]>


Thanks,
pq

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