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avcodec/mpeg12dec: Don't count errors from first thread twice

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Compilers can not perform this optimization on their own
given that they don't know that the different thread_context
pointers don't alias.
Also avoid using sequentially consistent operations with
atomics when only a single thread accesses them.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt
2025-03-01 22:36:35 +01:00
parent 094c2e7f5b
commit 4d8b706b1d
1 changed files with 11 additions and 3 deletions
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14
libavcodec/mpeg12dec.c
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@ -29,6 +29,7 @@
#define UNCHECKED_BITSTREAM_READER 1
#include <inttypes.h>
#include <stdatomic.h>
#include "libavutil/attributes.h"
#include "libavutil/emms.h"
@ -46,7 +47,6 @@
#include "hwaccel_internal.h"
#include "hwconfig.h"
#include "idctdsp.h"
#include "internal.h"
#include "mpeg_er.h"
#include "mpeg12.h"
#include "mpeg12codecs.h"
@ -2252,6 +2252,7 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
if (HAVE_THREADS &&
(avctx->active_thread_type & FF_THREAD_SLICE) &&
!avctx->hwaccel) {
int error_count = 0;
int i;
av_assert0(avctx->thread_count > 1);
@ -2259,7 +2260,10 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
&s2->thread_context[0], NULL,
s->slice_count, sizeof(void *));
for (i = 0; i < s->slice_count; i++)
s2->er.error_count += s2->thread_context[i]->er.error_count;
error_count += atomic_load_explicit(&s2->thread_context[i]->er.error_count,
memory_order_relaxed);
atomic_store_explicit(&s2->er.error_count, error_count,
memory_order_relaxed);
}
ret = slice_end(avctx, picture, got_output);
@ -2321,13 +2325,17 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
}
if (HAVE_THREADS && (avctx->active_thread_type & FF_THREAD_SLICE) &&
!avctx->hwaccel && s->slice_count) {
int error_count = 0;
int i;
avctx->execute(avctx, slice_decode_thread,
s2->thread_context, NULL,
s->slice_count, sizeof(void *));
for (i = 0; i < s->slice_count; i++)
s2->er.error_count += s2->thread_context[i]->er.error_count;
error_count += atomic_load_explicit(&s2->thread_context[i]->er.error_count,
memory_order_relaxed);
atomic_store_explicit(&s2->er.error_count, error_count,
memory_order_relaxed);
s->slice_count = 0;
}
if (last_code == 0 || last_code == SLICE_MIN_START_CODE) {