[vlc-devel] [PATCH 10/13] decoder: avoid unlock/lock when we don't need to

[Thomas Guillem]

On Mon, Sep 2, 2019, at 16:20, Steve Lhomme wrote:
> The p_vout/p_aout are flushed under lock in other places and they are modified
> under lock so need to be read under lock.

vout and aout have their own locks.

The thread calling DecoderPlayVideo() is the thread that created the vout (via decoder_UpdateVideoFormat()), so it does not need to lock to get the vout variable.

> ---
>  src/input/decoder.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/src/input/decoder.c b/src/input/decoder.c
> index f82e608ad4..24061a6618 100644
> --- a/src/input/decoder.c
> +++ b/src/input/decoder.c
> @@ -976,7 +976,6 @@ static void DecoderQueueCc( decoder_t *p_videodec, 
> block_t *p_cc,
>  static int DecoderPlayVideo_internal( struct decoder_owner *p_owner, 
> picture_t *p_picture )
>  {
>      decoder_t *p_dec = &p_owner->dec;
> -    vout_thread_t  *p_vout = p_owner->p_vout;
>  
>      if( p_picture->date == VLC_TICK_INVALID )
>          /* FIXME: VLC_TICK_INVALID -- verify video_output */
> @@ -996,19 +995,16 @@ static int DecoderPlayVideo_internal( struct 
> decoder_owner *p_owner, picture_t *
>      }
>  
>      p_owner->i_preroll_end = (vlc_tick_t)INT64_MIN;
> -    vlc_mutex_unlock( &p_owner->lock );
>  
>      if( unlikely(prerolled) )
>      {
>          msg_Dbg( p_dec, "end of video preroll" );
>  
> -        if( p_vout )
> -            vout_FlushAll( p_vout );
> +        if( p_owner->p_vout )
> +            vout_FlushAll( p_owner->p_vout );
>      }
>  
>      /* */
> -    vlc_mutex_lock( &p_owner->lock );
> -
>      if( p_owner->b_waiting && !p_owner->b_first )
>      {
>          p_owner->b_has_data = true;
> @@ -1025,6 +1021,7 @@ static int DecoderPlayVideo_internal( struct 
> decoder_owner *p_owner, picture_t *
>          p_picture->b_force = true;
>      }
>  
> +    vout_thread_t  *p_vout = p_owner->p_vout;
>      vlc_mutex_unlock( &p_owner->lock );
>  
>      /* FIXME: The *input* FIFO should not be locked here. This will 
> not work
> @@ -1128,7 +1125,6 @@ static int DecoderPlayAudio_internal( struct 
> decoder_owner *p_owner, block_t *p_
>      }
>  
>      p_owner->i_preroll_end = (vlc_tick_t)INT64_MIN;
> -    vlc_mutex_unlock( &p_owner->lock );
>  
>      if( unlikely(prerolled) )
>      {
> @@ -1139,8 +1135,6 @@ static int DecoderPlayAudio_internal( struct 
> decoder_owner *p_owner, block_t *p_
>      }
>  
>      /* */
> -    /* */
> -    vlc_mutex_lock( &p_owner->lock );
>      if( p_owner->b_waiting )
>      {
>          p_owner->b_has_data = true;
> @@ -1149,9 +1143,9 @@ static int DecoderPlayAudio_internal( struct 
> decoder_owner *p_owner, block_t *p_
>  
>      /* */
>      DecoderWaitUnblock_internal( p_owner );
> -    vlc_mutex_unlock( &p_owner->lock );
>  
>      audio_output_t *p_aout = p_owner->p_aout;
> +    vlc_mutex_unlock( &p_owner->lock );
>  
>      if( p_aout != NULL )
>      {
> -- 
> 2.17.1
> 
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