[FFmpeg-devel] [PATCH] dirac: make initialization of arithmetic coder tables threadsafe.

[Rostislav Pehlivanov]

On 27 March 2017 at 15:09, Ronald S. Bultje <rsbultje at gmail.com> wrote:

> ---
>  libavcodec/dirac_arith.c | 17 +++++++++++------
>  libavcodec/dirac_arith.h |  1 +
>  libavcodec/diracdec.c    |  9 ++++++++-
>  3 files changed, 20 insertions(+), 7 deletions(-)
>
> diff --git a/libavcodec/dirac_arith.c b/libavcodec/dirac_arith.c
> index bf91392..49c0909 100644
> --- a/libavcodec/dirac_arith.c
> +++ b/libavcodec/dirac_arith.c
> @@ -83,9 +83,19 @@ const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT] = {
>
>  int16_t ff_dirac_prob_branchless[256][2];
>
> -void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int
> length)
> +av_cold void ff_dirac_init_arith_tables(void)
>  {
>      int i;
> +
> +    for (i = 0; i < 256; i++) {
> +        ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
> +        ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
> +    }
> +}
> +
> +void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int
> length)
> +{
> +    int i, ret;
>      align_get_bits(gb);
>
>      length = FFMIN(length, get_bits_left(gb)/8);
> @@ -106,11 +116,6 @@ void ff_dirac_init_arith_decoder(DiracArith *c,
> GetBitContext *gb, int length)
>      c->counter = -16;
>      c->range   = 0xffff;
>
> -    for (i = 0; i < 256; i++) {
> -        ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
> -        ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
> -    }
> -
>      for (i = 0; i < DIRAC_CTX_COUNT; i++)
>          c->contexts[i] = 0x8000;
>  }
> diff --git a/libavcodec/dirac_arith.h b/libavcodec/dirac_arith.h
> index 003430a..24a7ca3 100644
> --- a/libavcodec/dirac_arith.h
> +++ b/libavcodec/dirac_arith.h
> @@ -190,6 +190,7 @@ static inline int dirac_get_arith_int(DiracArith *c,
> int follow_ctx, int data_ct
>      return ret;
>  }
>
> +void ff_dirac_init_arith_tables(void);
>  void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int
> length);
>
>  #endif /* AVCODEC_DIRAC_ARITH_H */
> diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
> index e0604af..202ae94 100644
> --- a/libavcodec/diracdec.c
> +++ b/libavcodec/diracdec.c
> @@ -26,6 +26,7 @@
>   * @author Marco Gerards <marco at gnu.org>, David Conrad, Jordi Ortiz <
> nenjordi at gmail.com>
>   */
>
> +#include "libavutil/thread.h"
>  #include "avcodec.h"
>  #include "get_bits.h"
>  #include "bytestream.h"
> @@ -379,10 +380,12 @@ static void free_sequence_buffers(DiracContext *s)
>      av_freep(&s->mcscratch);
>  }
>
> +static AVOnce dirac_arith_init = AV_ONCE_INIT;
> +
>  static av_cold int dirac_decode_init(AVCodecContext *avctx)
>  {
>      DiracContext *s = avctx->priv_data;
> -    int i;
> +    int i, ret;
>
>      s->avctx = avctx;
>      s->frame_number = -1;
> @@ -404,6 +407,9 @@ static av_cold int dirac_decode_init(AVCodecContext
> *avctx)
>              return AVERROR(ENOMEM);
>          }
>      }
> +    ret = ff_thread_once(&dirac_arith_init, ff_dirac_init_arith_tables);
> +    if (ret != 0)
> +        return AVERROR_UNKNOWN;
>
>      return 0;
>  }
> @@ -2299,5 +2305,6 @@ AVCodec ff_dirac_decoder = {
>      .close          = dirac_decode_end,
>      .decode         = dirac_decode_frame,
>      .capabilities   = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_SLICE_THREADS |
> AV_CODEC_CAP_DR1,
> +    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
>      .flush          = dirac_decode_flush,
>  };
> --
> 2.8.1
>
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>

LGTM, feel free to apply