[vlc-devel] [RFC PATCH 2/2] decoder: interruptible mwait

[Rémi Denis-Courmont]

On Monday 30 November 2015 14:57:49 Thomas Guillem wrote:
> A recent error in srt parsing lead the SPU DecoderThread to wait for
> 160000sec before displaying an spu. Therefore, you had to wait for that
> time when closing or flushing this decoder.
> 
> mwait (called from Audio and SPU DecoderThread) can now be interrupted when
> flushing or closing.
> 
> There is no check for this deadline. Maybe we should also test it in order
> to not exceed a certain value (more than 3seconds ?).
> ---
>  src/input/decoder.c | 40 +++++++++++++++++++++++++++++++++-------
>  1 file changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/src/input/decoder.c b/src/input/decoder.c
> index 0f08198..f7f9d0c 100644
> --- a/src/input/decoder.c
> +++ b/src/input/decoder.c
> @@ -107,6 +107,7 @@ struct decoder_owner_sys_t
>      bool b_waiting;
>      bool b_first;
>      bool b_has_data;
> +    mtime_t wait_deadline;
> 
>      /* Flushing */
>      bool flushing;
> @@ -619,6 +620,23 @@ static void DecoderWaitUnblock( decoder_t *p_dec )
>      }
>  }
> 
> +/* DecoderTimedWait: Interruptible wait
> + * Returns VLC_SUCCESS if wait was not interrupted, and VLC_EGENERIC
> otherwise */ +static int DecoderTimedWait( decoder_t *p_dec, mtime_t
> deadline ) +{
> +    decoder_owner_sys_t *p_owner = p_dec->p_owner;
> +
> +    vlc_assert_locked( &p_owner->lock );
> +    p_owner->wait_deadline = deadline;
> +
> +    int ret = 0;
> +    while( p_owner->wait_deadline > 0 && ret != ETIMEDOUT )
> +        ret = vlc_cond_timedwait( &p_owner->wait_request, &p_owner->lock,
> +                                  p_owner->wait_deadline );
> +
> +    return ret == ETIMEDOUT ? VLC_SUCCESS : VLC_EGENERIC;
> +}
> +
>  static inline void DecoderUpdatePreroll( int64_t *pi_preroll, const block_t
> *p ) {
>      if( p->i_flags & (BLOCK_FLAG_PREROLL|BLOCK_FLAG_DISCONTINUITY) )
> @@ -1016,21 +1034,21 @@ static void DecoderPlayAudio( decoder_t *p_dec,
> block_t *p_audio, DecoderWaitUnblock( p_dec );
>      DecoderFixTs( p_dec, &p_audio->i_pts, NULL, &p_audio->i_length,
>                    &i_rate, AOUT_MAX_ADVANCE_TIME );
> -    vlc_mutex_unlock( &p_owner->lock );
> 
>      audio_output_t *p_aout = p_owner->p_aout;
> 
>      if( p_aout == NULL || p_audio->i_pts <= VLC_TS_INVALID
> 
>       || i_rate < INPUT_RATE_DEFAULT/AOUT_MAX_INPUT_RATE
> 
> -     || i_rate > INPUT_RATE_DEFAULT*AOUT_MAX_INPUT_RATE )
> +     || i_rate > INPUT_RATE_DEFAULT*AOUT_MAX_INPUT_RATE
> +     || DecoderTimedWait( p_dec, p_audio->i_pts - AOUT_MAX_PREPARE_TIME ) )
> {
> +        vlc_mutex_unlock( &p_owner->lock );
>          msg_Dbg( p_dec, "discarded audio buffer" );
>          *pi_lost_sum += 1;
>          block_Release( p_audio );
>          return;
>      }
> -
> -    mwait( p_audio->i_pts - AOUT_MAX_PREPARE_TIME );
> +    vlc_mutex_unlock( &p_owner->lock );
> 
>      if( aout_DecPlay( p_aout, p_audio, i_rate ) == 0 )
>          *pi_played_sum += 1;
> @@ -1154,15 +1172,16 @@ static void DecoderPlaySpu( decoder_t *p_dec,
> subpicture_t *p_subpic ) DecoderWaitUnblock( p_dec );
>      DecoderFixTs( p_dec, &p_subpic->i_start, &p_subpic->i_stop, NULL,
>                    NULL, INT64_MAX );
> -    vlc_mutex_unlock( &p_owner->lock );
> 
> -    if( p_subpic->i_start <= VLC_TS_INVALID )
> +    if( p_subpic->i_start <= VLC_TS_INVALID
> +     || DecoderTimedWait( p_dec, p_subpic->i_start - SPU_MAX_PREPARE_TIME )
> ) {
> +        vlc_mutex_unlock( &p_owner->lock );
>          subpicture_Delete( p_subpic );
>          return;
>      }
> +    vlc_mutex_unlock( &p_owner->lock );
> 
> -    mwait( p_subpic->i_start - SPU_MAX_PREPARE_TIME );
>      vout_PutSubpicture( p_vout, p_subpic );
>  }
> 
> @@ -1483,6 +1502,7 @@ static decoder_t * CreateDecoder( vlc_object_t
> *p_parent, p_owner->b_draining = false;
>      atomic_init( &p_owner->drained, false );
>      p_owner->b_idle = false;
> +    p_owner->wait_deadline = 0;
> 
>      es_format_Init( &p_owner->fmt, UNKNOWN_ES, 0 );
> 
> @@ -1760,6 +1780,7 @@ void input_DecoderDelete( decoder_t *p_dec )
>      /* Make sure we aren't waiting/decoding anymore */
>      vlc_mutex_lock( &p_owner->lock );
>      p_owner->b_waiting = false;
> +    p_owner->wait_deadline = 0;
>      vlc_cond_signal( &p_owner->wait_request );

See below.

> 
>      /* If the video output is paused or too slow, the decoded picture FIFO
> may @@ -1891,6 +1912,11 @@ void input_DecoderFlush( decoder_t *p_dec )
> vlc_fifo_Signal( p_owner->p_fifo );
> 
>      vlc_fifo_Unlock( p_owner->p_fifo );
> +
> +    vlc_mutex_lock( &p_owner->lock );
> +    p_owner->wait_deadline = 0;
> +    vlc_cond_signal( &p_owner->wait_request );
> +    vlc_mutex_unlock( &p_owner->lock );
>  }

Are you sure that works if input_DecoderFlush() is called *before* 
DecoderTimedWait()? I think it just gets stuck as without the patch.

>  void input_DecoderIsCcPresent( decoder_t *p_dec, bool pb_present[4] )

-- 
Rémi Denis-Courmont
http://www.remlab.net/