Andreas Rheinhardt:
> jpeg2000_decode_tile() (which is run concurrently by several threads
> when using slice threading) currently modifies some joint values
> before doing its actual work. This is a data race that happens to work
> because all threads set the same values; but it is nevertheless
> undefined behaviour.
>
> Fix this by performing said preparatory work in the main thread instead.
> This fixes the vsynth(1|2|_lena)-jpeg2000(-97)? FATE-tests when using
> TSAN and slice threading.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com>
> ---
> libavcodec/jpeg2000dec.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
> index 80b2e2d627..a7eb809f30 100644
> --- a/libavcodec/jpeg2000dec.c
> +++ b/libavcodec/jpeg2000dec.c
> @@ -2080,7 +2080,6 @@ static int jpeg2000_decode_tile(AVCodecContext *avctx,
> void *td,
> Jpeg2000DecoderContext *s = avctx->priv_data;
> AVFrame *picture = td;
> Jpeg2000Tile *tile = s->tile + jobnr;
> - int x;
>
> tile_codeblocks(s, tile);
>
> @@ -2088,17 +2087,6 @@ static int jpeg2000_decode_tile(AVCodecContext *avctx,
> void *td,
> if (tile->codsty[0].mct)
> mct_decode(s, tile);
>
> - for (x = 0; x < s->ncomponents; x++) {
> - if (s->cdef[x] < 0) {
> - for (x = 0; x < s->ncomponents; x++) {
> - s->cdef[x] = x + 1;
> - }
> - if ((s->ncomponents & 1) == 0)
> - s->cdef[s->ncomponents-1] = 0;
> - break;
> - }
> - }
> -
> if (s->precision <= 8) {
> write_frame_8(s, tile, picture, 8);
> } else {
> @@ -2537,6 +2525,17 @@ static int jpeg2000_decode_frame(AVCodecContext
> *avctx, void *data,
> if (ret = jpeg2000_read_bitstream_packets(s))
> goto end;
>
> + for (int x = 0; x < s->ncomponents; x++) {
> + if (s->cdef[x] < 0) {
> + for (x = 0; x < s->ncomponents; x++) {
> + s->cdef[x] = x + 1;
> + }
> + if ((s->ncomponents & 1) == 0)
> + s->cdef[s->ncomponents-1] = 0;
> + break;
> + }
> + }
> +
> avctx->execute2(avctx, jpeg2000_decode_tile, picture, NULL, s->numXtiles
> * s->numYtiles);
>
> jpeg2000_dec_cleanup(s);
Will apply this patch tomorrow unless there are objections.
- Andreas
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