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avcodec/jpeg2000dec: Move preparations to main thread, fix race 

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.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2022-01-27 15:53:48 +01:00
parent e13f0b9456
commit 218d1f76d4
1 changed files with 11 additions and 12 deletions
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23
libavcodec/jpeg2000dec.c
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@ -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);