[Mesa-dev] [PATCH 9/9] loader_dri3: Make sure we have an updated back v2

[Thomas Hellstrom]

On 08/15/2017 08:32 PM, Thomas Hellstrom wrote:
> With GLX_SWAP_COPY_OML and GLX_SWAP_EXCHANGE_OML it may happen in situations
> when glXSwapBuffers() is immediately followed by for example another
> glXSwapBuffers() or glXCopyBuffers() or back buffer age querying, that we
> haven't yet allocated and initialized a new back buffer because there was
> no GL rendering in between.
>
> Make sure that we have a back buffer in those situations.
>
> v2: Eliminate the drawable have_back_format member.
>
> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
> ---
>   src/loader/loader_dri3_helper.c | 62 ++++++++++++++++++++++++++++++++++-------
>   src/loader/loader_dri3_helper.h |  1 +
>   2 files changed, 53 insertions(+), 10 deletions(-)
>
> diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
> index 55e1471..a2885ac 100644
> --- a/src/loader/loader_dri3_helper.c
> +++ b/src/loader/loader_dri3_helper.c
> @@ -59,6 +59,9 @@ static struct loader_dri3_blit_context blit_context = {
>   static void
>   dri3_flush_present_events(struct loader_dri3_drawable *draw);
>   
> +static struct loader_dri3_buffer *
> +dri3_find_back_alloc(struct loader_dri3_drawable *draw);
> +
>   /**
>    * Do we have blit functionality in the image blit extension?
>    *
> @@ -269,6 +272,7 @@ loader_dri3_drawable_init(xcb_connection_t *conn,
>      draw->first_init = true;
>   
>      draw->cur_blit_source = -1;
> +   draw->back_format = __DRI_IMAGE_FORMAT_NONE;
>   
>      if (draw->ext->config)
>         draw->ext->config->configQueryi(draw->dri_screen,
> @@ -616,7 +620,10 @@ loader_dri3_copy_sub_buffer(struct loader_dri3_drawable *draw,
>         flags |= __DRI2_FLUSH_CONTEXT;
>      loader_dri3_flush(draw, flags, __DRI2_THROTTLE_SWAPBUFFER);
>   
> -   back = dri3_back_buffer(draw);
> +   back = dri3_find_back_alloc(draw);
> +   if (!back)
> +      return;
> +
>      y = draw->height - y - height;
>   
>      if (draw->is_different_gpu) {
> @@ -641,7 +648,7 @@ loader_dri3_copy_sub_buffer(struct loader_dri3_drawable *draw,
>      loader_dri3_swapbuffer_barrier(draw);
>      dri3_fence_reset(draw->conn, back);
>      dri3_copy_area(draw->conn,
> -                  dri3_back_buffer(draw)->pixmap,
> +                  back->pixmap,
>                     draw->drawable,
>                     dri3_drawable_gc(draw),
>                     x, y, x, y, width, height);
> @@ -652,7 +659,7 @@ loader_dri3_copy_sub_buffer(struct loader_dri3_drawable *draw,
>      if (draw->have_fake_front && !draw->is_different_gpu) {
>         dri3_fence_reset(draw->conn, dri3_fake_front_buffer(draw));
>         dri3_copy_area(draw->conn,
> -                     dri3_back_buffer(draw)->pixmap,
> +                     back->pixmap,
>                        dri3_fake_front_buffer(draw)->pixmap,
>                        dri3_drawable_gc(draw),
>                        x, y, x, y, width, height);
> @@ -763,7 +770,8 @@ loader_dri3_swap_buffers_msc(struct loader_dri3_drawable *draw,
>   
>      draw->vtable->flush_drawable(draw, flush_flags);
>   
> -   back = draw->buffers[dri3_find_back(draw)];
> +   back = dri3_find_back_alloc(draw);
> +
>      if (draw->is_different_gpu && back) {
>         /* Update the linear buffer before presenting the pixmap */
>         (void) loader_dri3_blit_image(draw,
> @@ -892,15 +900,12 @@ loader_dri3_swap_buffers_msc(struct loader_dri3_drawable *draw,
>   int
>   loader_dri3_query_buffer_age(struct loader_dri3_drawable *draw)
>   {
> -   int back_id = LOADER_DRI3_BACK_ID(dri3_find_back(draw));
> +   struct loader_dri3_buffer *back = dri3_find_back_alloc(draw);
>   
> -   if (back_id < 0 || !draw->buffers[back_id])
> +   if (!back || back->last_swap == 0)
>         return 0;
>   
> -   if (draw->buffers[back_id]->last_swap != 0)
> -      return draw->send_sbc - draw->buffers[back_id]->last_swap + 1;
> -   else
> -      return 0;
> +   return draw->send_sbc - back->last_swap + 1;
>   }
>   
>   /** loader_dri3_open
> @@ -1334,6 +1339,8 @@ dri3_get_buffer(__DRIdrawable *driDrawable,
>      int buf_id;
>   
>      if (buffer_type == loader_dri3_buffer_back) {
> +      draw->back_format = format;
> +
>         buf_id = dri3_find_back(draw);
>   
>         if (buf_id < 0)
> @@ -1620,3 +1627,38 @@ loader_dri3_close_screen(__DRIscreen *dri_screen)
>      }
>      mtx_unlock(&blit_context.mtx);
>   }
> +
> +/**
> + * Find a backbuffer slot - potentially allocating a back buffer
> + *
> + * \param draw[in,out]  Pointer to the drawable for which to find back.
> + * \return Pointer to a new back buffer or NULL if allocation failed or was
> + * not mandated.
> + *
> + * Find a potentially new back buffer, and if it's not been allocated yet and
> + * in addition needs initializing, then try to allocate and initialize it.
> + */
> +static struct loader_dri3_buffer *
> +dri3_find_back_alloc(struct loader_dri3_drawable *draw)
> +{
> +   struct loader_dri3_buffer *back;
> +   int id;
> +
> +   id = dri3_find_back(draw);
> +   back = (id >= 0) ? draw->buffers[id] : NULL;
> +
> +   if (!back && draw->back_format != __DRI_IMAGE_FORMAT_NONE) {
> +      (void) dri3_get_buffer(draw->dri_drawable,
> +                             draw->back_format,
> +                             loader_dri3_buffer_back,
> +                             draw);
> +   } else if (back) {

Actually, if we end up here on a glXSwapBuffer immediately followed by a 
glXSwapBuffer, a local back-preserving copy will not take place. We need 
to call dri3_get_buffer() here as well. Will send out a v3 for reference.

/Thomas