[Mesa-dev] [PATCH v2] dri3: Prevent multiple freeing of buffers.

[Michel Dänzer]

On 2018-04-10 09:44 AM, Sergii Romantsov wrote:
> Commit 3160cb86aa92 adds optimization with flag 'reallocate'.
> Processing of flag causes buffers freeing while pointer
> is still hold in caller stack and than again used to be freed.
> 
> Fixes: 3160cb86aa92 "egl/x11: Re-allocate buffers if format is suboptimal"
> 
> v2:
>  used flag 'busy' instead of introducing new one.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=105906
> Signed-off-by: Sergii Romantsov <sergii.romantsov at globallogic.com>
> Tested-by: Andriy Khulap <andriy.khulap at globallogic.com>
> ---
>  src/loader/loader_dri3_helper.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
> index fe17df1..a934db1 100644
> --- a/src/loader/loader_dri3_helper.c
> +++ b/src/loader/loader_dri3_helper.c
> @@ -1688,6 +1688,7 @@ dri3_get_buffer(__DRIdrawable *driDrawable,
>             (buffer_type == loader_dri3_buffer_front && draw->have_fake_front))
>            && buffer) {
>  
> +         buffer->busy = true;
>           /* Fill the new buffer with data from an old buffer */
>           dri3_fence_await(draw->conn, draw, buffer);
>           if (!loader_dri3_blit_image(draw,

This seems a bit of a hack. Will this always be cleared again, in
particular if it's the fake front buffer?


> @@ -1731,6 +1732,7 @@ dri3_get_buffer(__DRIdrawable *driDrawable,
>        draw->buffers[buf_id] = buffer;
>     }
>     dri3_fence_await(draw->conn, draw, buffer);
> +   buffer = draw->buffers[buf_id];

This should be something like

   if (buffer_type == loader_dri3_buffer_back) {
      buf_id = dri3_find_back(draw);

      if (buf_id < 0)
         return NULL;
   }
   buffer = draw->buffers[buf_id];

to get the now-current back buffer.


> @@ -1744,7 +1746,8 @@ dri3_get_buffer(__DRIdrawable *driDrawable,
>     if (buffer_type == loader_dri3_buffer_back &&
>         draw->cur_blit_source != -1 &&
>         draw->buffers[draw->cur_blit_source] &&
> -       buffer != draw->buffers[draw->cur_blit_source]) {
> +       buffer != draw->buffers[draw->cur_blit_source] &&
> +       buffer != NULL) {
>  
>        struct loader_dri3_buffer *source = draw->buffers[draw->cur_blit_source];
>  
> 

With the above, this NULL guard isn't needed.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer