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

[Rémi Denis-Courmont]

Hi,

T1 sets, say, A/R, which updates the window size. Then T2 does the same. Then T2 sends the A/R control to vout thread, then T1 sends the same.

-> window uses T2 A/R, display uses T1 A/R.

Le 13 juin 2019 19:15:20 GMT+08:00, Steve Lhomme <robux4 at ycbcr.xyz> a écrit :
>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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