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avcodec: Fix invalid uses of ff_codec_open2_recursive()

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Normally no two codecs with FF_CODEC_CAP_INIT_THREADSAFE unset
can be initialized at the same time: a mutex in avcodec_open2()
ensures this. This implies that one cannot simply open a codec
with a non-threadsafe init-function from the init function of
a codec whose own init function is not threadsafe either as the child
codec couldn't acquire the lock.

ff_codec_open2_recursive() exists to get around this limitation:
If the init function of the child codec to be initialized is not
thread-safe, the mutex is unlocked, the child is initialized and
the mutex is locked again. This of course has as a prerequisite that
the parent AVCodecContext actually holds the lock, i.e. that the
parent codec's init function is not thread-safe. If it is, then one
can (and has to) just use avcodec_open2() directly (if the child's
init function is not thread-safe, then avcodec_open2() will have to
acquire the mutex itself (and potentially wait for it), so that it is
perfectly fine for an otherwise thread-safe init function to open
a codec with a potentially non-thread-safe init function via
avcodec_open2()).

Yet several of the users of ff_codec_open2_recursive() have the
FF_CODEC_CAP_INIT_THREADSAFE flag set; this only worked because
all the child codecs' init functions were thread-safe themselves
so that ff_codec_open2_recursive() didn't touch the mutex at all.
But of course the real solution to this is to directly use
avcodec_open2().

Reviewed-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
This commit is contained in:
Andreas Rheinhardt 2020-11-26 23:16:04 +01:00
parent 9de6688cc4
commit 4e1fee405f
3 changed files with 4 additions and 4 deletions
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2
libavcodec/avrndec.c
View File

@ -65,7 +65,7 @@ static av_cold int init(AVCodecContext *avctx)
a->mjpeg_avctx->width = avctx->width;
a->mjpeg_avctx->height = avctx->height;
if ((ret = ff_codec_open2_recursive(a->mjpeg_avctx, codec, &thread_opt)) < 0) {
if ((ret = avcodec_open2(a->mjpeg_avctx, codec, &thread_opt)) < 0) {
av_log(avctx, AV_LOG_ERROR, "MJPEG codec failed to open\n");
}
av_dict_free(&thread_opt);

4
libavcodec/imm5.c
View File

@ -63,7 +63,7 @@ static av_cold int imm5_init(AVCodecContext *avctx)
ctx->h264_avctx->thread_count = 1;
ctx->h264_avctx->flags = avctx->flags;
ctx->h264_avctx->flags2 = avctx->flags2;
ret = ff_codec_open2_recursive(ctx->h264_avctx, codec, NULL);
ret = avcodec_open2(ctx->h264_avctx, codec, NULL);
if (ret < 0)
return ret;
@ -76,7 +76,7 @@ static av_cold int imm5_init(AVCodecContext *avctx)
ctx->hevc_avctx->thread_count = 1;
ctx->hevc_avctx->flags = avctx->flags;
ctx->hevc_avctx->flags2 = avctx->flags2;
ret = ff_codec_open2_recursive(ctx->hevc_avctx, codec, NULL);
ret = avcodec_open2(ctx->hevc_avctx, codec, NULL);
if (ret < 0)
return ret;

2
libavcodec/tdsc.c
View File

@ -125,7 +125,7 @@ static av_cold int tdsc_init(AVCodecContext *avctx)
ctx->jpeg_avctx->flags2 = avctx->flags2;
ctx->jpeg_avctx->dct_algo = avctx->dct_algo;
ctx->jpeg_avctx->idct_algo = avctx->idct_algo;
ret = ff_codec_open2_recursive(ctx->jpeg_avctx, codec, NULL);
ret = avcodec_open2(ctx->jpeg_avctx, codec, NULL);
if (ret < 0)
return ret;