[Spice-devel] [PATCH spice-gtk 2/3] decode-glz: Handle needing glz images before they have arrived

[Marc-André Lureau]

ack

----- Original Message -----
> With multi monitor guests, it is possible for a glz-image to refer to
> bits from another glz-image which has not arrived yet! This can
> happen
> because each monitor has its own display channel, and thus its own
> socket,
> but they share the glz dict. Thus things can arrive out of order,
> with a
> glz-image on display 1 arriving before the glz-image on display 2
> which it
> refers too.
> 
> This triggers the:
> g_return_val_if_fail(w->images[slot]->hdr.id == id - dist, NULL);
> 
> In glz_decoder_window_bits(), which is what caused me to debug this,
> once
> the out order thing was clear, so was the fix.
> If w->images[slot]->hdr.id == id - dist is not true, we need to wait
> for the
> correct image to arrive.
> 
> The out of order issue with multiple monitors can also trigger the
> g_warn_if_reached() in glz_decoder_window_resize(), so remove that.
> 
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  gtk/decode-glz.c |   21 ++++++++++++---------
>  1 files changed, 12 insertions(+), 9 deletions(-)
> 
> diff --git a/gtk/decode-glz.c b/gtk/decode-glz.c
> index 8ddb9d8..317fa9e 100644
> --- a/gtk/decode-glz.c
> +++ b/gtk/decode-glz.c
> @@ -95,8 +95,12 @@ static void
> glz_decoder_window_resize(SpiceGlzDecoderWindow *w)
>      new_images = spice_new0(struct glz_image*, w->nimages * 2);
>      for (i = 0; i < w->nimages; i++) {
>          if (w->images[i] == NULL) {
> -            /* FIXME: is this really an anormal condition? */
> -            g_warn_if_reached();
> +            /*
> +             * We can have empty slots when images come in out of
> order, this
> +             * can happen when a vm has multiple displays, since
> each display
> +             * uses its own socket there is no guarantee that images
> +             * originating from different displays are received in
> id order.
> +             */
>              continue;
>          }
>          new_slot = w->images[i]->hdr.id % (w->nimages * 2);
> @@ -124,14 +128,14 @@ static void
> glz_decoder_window_add(SpiceGlzDecoderWindow *w,
>  struct wait_for_image_data {
>      SpiceGlzDecoderWindow     *window;
>      uint64_t                   id;
> -    uint32_t                   dist;
>  };
>  
>  static gboolean wait_for_image(gpointer data)
>  {
>      struct wait_for_image_data *wait = data;
> -    int slot = (wait->id - wait->dist) % wait->window->nimages;
> -    gboolean ready = wait->window->images[slot] != NULL;
> +    int slot = wait->id % wait->window->nimages;
> +    struct glz_image *image = wait->window->images[slot];
> +    gboolean ready = image && image->hdr.id == wait->id;
>  
>      SPICE_DEBUG("image with slot %d: %s", slot, ready ? "yes" :
>      "no");
>  
> @@ -142,12 +146,11 @@ static void
> *glz_decoder_window_bits(SpiceGlzDecoderWindow *w, uint64_t id,
>                                       uint32_t dist, uint32_t offset)
>  {
>      int slot = (id - dist) % w->nimages;
> -
> -    if (!w->images[slot]) {
> +
> +    if (!w->images[slot] || w->images[slot]->hdr.id != id - dist) {
>          struct wait_for_image_data data = {
>              .window = w,
> -            .id = id,
> -            .dist = dist,
> +            .id = id - dist,
>          };
>  
>          g_condition_wait(wait_for_image, &data);
> --
> 1.7.6.4
> 
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