[vlc-devel] [PATCH 05/13] vout: set display filled synchronously

[Steve Lhomme]

On 2019-06-12 19:48, Rémi Denis-Courmont wrote:
> This fixes an ABBA race if two threads set the flag simultaneously.

What is an ABBA race ?
Did you mean this ? https://en.wikipedia.org/wiki/ABA_problem

> ---
>   src/video_output/control.h      |  1 -
>   src/video_output/video_output.c | 12 +++++-------
>   2 files changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/src/video_output/control.h b/src/video_output/control.h
> index b189b6478a..a384afa2c6 100644
> --- a/src/video_output/control.h
> +++ b/src/video_output/control.h
> @@ -32,7 +32,6 @@ enum {
>   
>       VOUT_CONTROL_MOUSE_STATE,           /* vlc_mouse_t */
>       VOUT_CONTROL_DISPLAY_SIZE,          /* window */
> -    VOUT_CONTROL_DISPLAY_FILLED,        /* bool */
>       VOUT_CONTROL_ZOOM,                  /* pair */
>   
>       VOUT_CONTROL_ASPECT_RATIO,          /* pair */
> diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
> index ca9831e086..af2c0ecf8d 100644
> --- a/src/video_output/video_output.c
> +++ b/src/video_output/video_output.c
> @@ -433,10 +433,13 @@ void vout_ChangeDisplayFilled(vout_thread_t *vout, bool is_filled)
>       vlc_mutex_lock(&sys->window_lock);
>       sys->display_cfg.is_display_filled = is_filled;
>       /* no window size update here */
> +
> +    vlc_mutex_lock(&sys->display_lock);
>       vlc_mutex_unlock(&sys->window_lock);

That looks like the kind of thing that may end up in a deadlock if not 
done consistently.

> -    vout_control_PushBool(&vout->p->control, VOUT_CONTROL_DISPLAY_FILLED,
> -                          is_filled);
> +    if (sys->display != NULL)
> +        vout_SetDisplayFilled(sys->display, is_filled);
> +    vlc_mutex_unlock(&sys->display_lock);
>   }
>   
>   void vout_ChangeZoom(vout_thread_t *vout, unsigned num, unsigned den)
> @@ -1573,11 +1576,6 @@ static void ThreadControl(vout_thread_t *vout, vout_control_cmd_t cmd)
>                                cmd.window.width, cmd.window.height);
>           vlc_mutex_unlock(&vout->p->display_lock);
>           break;
> -    case VOUT_CONTROL_DISPLAY_FILLED:
> -        vlc_mutex_lock(&vout->p->display_lock);
> -        vout_SetDisplayFilled(vout->p->display, cmd.boolean);
> -        vlc_mutex_unlock(&vout->p->display_lock);
> -        break;
>       case VOUT_CONTROL_ZOOM:
>           vlc_mutex_lock(&vout->p->display_lock);
>           vout_SetDisplayZoom(vout->p->display, cmd.pair.a, cmd.pair.b);
> -- 
> 2.20.1
> 
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