[FFmpeg-devel] [PATCH] avcodec: deprecate thread_safe_callbacks
Anton Khirnov
anton at khirnov.net
Tue Aug 4 14:59:42 EEST 2020
They add considerable complexity to frame-threading implementation,
which includes an unavoidably leaking error path, while the advantages
of this option to the users are highly dubious.
It should be always possible and desirable for the callers to make their
get_buffer2() implementation thread-safe, so deprecate this option.
---
doc/APIchanges | 4 +++
doc/multithreading.txt | 3 +-
fftools/ffmpeg.c | 2 ++
libavcodec/avcodec.h | 7 ++++
libavcodec/pthread_frame.c | 69 +++++++++++++++++++++++++++++++++++---
libavcodec/thread.h | 4 +++
libavcodec/utils.c | 13 +++++++
libavcodec/version.h | 3 ++
8 files changed, 99 insertions(+), 6 deletions(-)
diff --git a/doc/APIchanges b/doc/APIchanges
index 208258be05..44167a602b 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -15,6 +15,10 @@ libavutil: 2017-10-21
API changes, most recent first:
+2020-xx-xx - xxxxxxxxxx - lavc 58.87.100 - avcodec.h
+ Deprecate AVCodecContext.thread_safe_callbacks. After the next major bump,
+ user callbacks must always be thread-safe when frame threading is used.
+
2020-xx-xx - xxxxxxxxxx - lavc 58.87.100 - avcodec.h codec_par.h
Move AVBitstreamFilter-related public API to new header bsf.h.
Move AVCodecParameters-related public API to new header codec_par.h.
diff --git a/doc/multithreading.txt b/doc/multithreading.txt
index 4f645dc147..470194ff85 100644
--- a/doc/multithreading.txt
+++ b/doc/multithreading.txt
@@ -20,8 +20,7 @@ Slice threading -
Frame threading -
* Restrictions with slice threading also apply.
-* For best performance, the client should set thread_safe_callbacks if it
- provides a thread-safe get_buffer() callback.
+* Custom get_buffer2() and get_format() callbacks must be thread-safe.
* There is one frame of delay added for every thread beyond the first one.
Clients must be able to handle this; the pkt_dts and pkt_pts fields in
AVFrame will work as usual.
diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index ad95a0e417..eed72b67f1 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -2883,7 +2883,9 @@ static int init_input_stream(int ist_index, char *error, int error_len)
ist->dec_ctx->opaque = ist;
ist->dec_ctx->get_format = get_format;
ist->dec_ctx->get_buffer2 = get_buffer;
+#if LIBAVCODEC_VERSION_MAJOR < 59
ist->dec_ctx->thread_safe_callbacks = 1;
+#endif
av_opt_set_int(ist->dec_ctx, "refcounted_frames", 1, 0);
if (ist->dec_ctx->codec_id == AV_CODEC_ID_DVB_SUBTITLE &&
diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index f10b7a06ec..2dec0d8ca0 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -1934,6 +1934,7 @@ typedef struct AVCodecContext {
*/
int active_thread_type;
+#if FF_API_THREAD_SAFE_CALLBACKS
/**
* Set by the client if its custom get_buffer() callback can be called
* synchronously from another thread, which allows faster multithreaded decoding.
@@ -1941,8 +1942,14 @@ typedef struct AVCodecContext {
* Ignored if the default get_buffer() is used.
* - encoding: Set by user.
* - decoding: Set by user.
+ *
+ * @deprecated the custom get_buffer2() callback should always be
+ * thread-safe. Thread-unsafe get_buffer2() implementations will be
+ * invalid once this field is removed.
*/
+ attribute_deprecated
int thread_safe_callbacks;
+#endif
/**
* The codec may call this to execute several independent things.
diff --git a/libavcodec/pthread_frame.c b/libavcodec/pthread_frame.c
index 64121f5a9a..75722e359e 100644
--- a/libavcodec/pthread_frame.c
+++ b/libavcodec/pthread_frame.c
@@ -89,6 +89,7 @@ typedef struct PerThreadContext {
atomic_int state;
+#if FF_API_THREAD_SAFE_CALLBACKS
/**
* Array of frames passed to ff_thread_release_buffer().
* Frames are released after all threads referencing them are finished.
@@ -102,6 +103,7 @@ typedef struct PerThreadContext {
const enum AVPixelFormat *available_formats; ///< Format array for get_format()
enum AVPixelFormat result_format; ///< get_format() result
+#endif
int die; ///< Set when the thread should exit.
@@ -137,8 +139,10 @@ typedef struct FrameThreadContext {
*/
} FrameThreadContext;
+#if FF_API_THREAD_SAFE_CALLBACKS
#define THREAD_SAFE_CALLBACKS(avctx) \
((avctx)->thread_safe_callbacks || (avctx)->get_buffer2 == avcodec_default_get_buffer2)
+#endif
static void async_lock(FrameThreadContext *fctx)
{
@@ -178,8 +182,14 @@ static attribute_align_arg void *frame_worker_thread(void *arg)
if (p->die) break;
- if (!codec->update_thread_context && THREAD_SAFE_CALLBACKS(avctx))
+FF_DISABLE_DEPRECATION_WARNINGS
+ if (!codec->update_thread_context
+#if FF_API_THREAD_SAFE_CALLBACKS
+ && THREAD_SAFE_CALLBACKS(avctx)
+#endif
+ )
ff_thread_finish_setup(avctx);
+FF_ENABLE_DEPRECATION_WARNINGS
/* If a decoder supports hwaccel, then it must call ff_get_format().
* Since that call must happen before ff_thread_finish_setup(), the
@@ -352,7 +362,11 @@ static int update_context_from_user(AVCodecContext *dst, AVCodecContext *src)
dst->frame_number = src->frame_number;
dst->reordered_opaque = src->reordered_opaque;
+#if FF_API_THREAD_SAFE_CALLBACKS
+FF_DISABLE_DEPRECATION_WARNINGS
dst->thread_safe_callbacks = src->thread_safe_callbacks;
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
if (src->slice_count && src->slice_offset) {
if (dst->slice_count < src->slice_count) {
@@ -368,6 +382,7 @@ static int update_context_from_user(AVCodecContext *dst, AVCodecContext *src)
return 0;
}
+#if FF_API_THREAD_SAFE_CALLBACKS
/// Releases the buffers that this decoding thread was the last user of.
static void release_delayed_buffers(PerThreadContext *p)
{
@@ -388,6 +403,7 @@ static void release_delayed_buffers(PerThreadContext *p)
pthread_mutex_unlock(&fctx->buffer_mutex);
}
}
+#endif
static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx,
AVPacket *avpkt)
@@ -411,7 +427,9 @@ static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx,
(p->avctx->debug & FF_DEBUG_THREADS) != 0,
memory_order_relaxed);
+#if FF_API_THREAD_SAFE_CALLBACKS
release_delayed_buffers(p);
+#endif
if (prev_thread) {
int err;
@@ -441,6 +459,8 @@ static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx,
pthread_cond_signal(&p->input_cond);
pthread_mutex_unlock(&p->mutex);
+#if FF_API_THREAD_SAFE_CALLBACKS
+FF_DISABLE_DEPRECATION_WARNINGS
/*
* If the client doesn't have a thread-safe get_buffer(),
* then decoding threads call back to the main thread,
@@ -474,6 +494,8 @@ static int submit_packet(PerThreadContext *p, AVCodecContext *user_avctx,
pthread_mutex_unlock(&p->progress_mutex);
}
}
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
fctx->prev_thread = p;
fctx->next_decoding++;
@@ -665,7 +687,10 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count)
{
FrameThreadContext *fctx = avctx->internal->thread_ctx;
const AVCodec *codec = avctx->codec;
- int i, j;
+ int i;
+#if FF_API_THREAD_SAFE_CALLBACKS
+ int j;
+#endif
park_frame_worker_threads(fctx, thread_count);
@@ -698,7 +723,9 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count)
if (codec->close && p->avctx)
codec->close(p->avctx);
+#if FF_API_THREAD_SAFE_CALLBACKS
release_delayed_buffers(p);
+#endif
av_frame_free(&p->frame);
}
@@ -712,9 +739,11 @@ void ff_frame_thread_free(AVCodecContext *avctx, int thread_count)
pthread_cond_destroy(&p->output_cond);
av_packet_unref(&p->avpkt);
+#if FF_API_THREAD_SAFE_CALLBACKS
for (j = 0; j < p->released_buffers_allocated; j++)
av_frame_free(&p->released_buffers[j]);
av_freep(&p->released_buffers);
+#endif
if (p->avctx) {
if (codec->priv_class)
@@ -892,7 +921,9 @@ void ff_thread_flush(AVCodecContext *avctx)
av_frame_unref(p->frame);
p->result = 0;
+#if FF_API_THREAD_SAFE_CALLBACKS
release_delayed_buffers(p);
+#endif
if (avctx->codec->flush)
avctx->codec->flush(p->avctx);
@@ -902,10 +933,16 @@ void ff_thread_flush(AVCodecContext *avctx)
int ff_thread_can_start_frame(AVCodecContext *avctx)
{
PerThreadContext *p = avctx->internal->thread_ctx;
+FF_DISABLE_DEPRECATION_WARNINGS
if ((avctx->active_thread_type&FF_THREAD_FRAME) && atomic_load(&p->state) != STATE_SETTING_UP &&
- (avctx->codec->update_thread_context || !THREAD_SAFE_CALLBACKS(avctx))) {
+ (avctx->codec->update_thread_context
+#if FF_API_THREAD_SAFE_CALLBACKS
+ || !THREAD_SAFE_CALLBACKS(avctx)
+#endif
+ )) {
return 0;
}
+FF_ENABLE_DEPRECATION_WARNINGS
return 1;
}
@@ -919,8 +956,14 @@ static int thread_get_buffer_internal(AVCodecContext *avctx, ThreadFrame *f, int
if (!(avctx->active_thread_type & FF_THREAD_FRAME))
return ff_get_buffer(avctx, f->f, flags);
+FF_DISABLE_DEPRECATION_WARNINGS
if (atomic_load(&p->state) != STATE_SETTING_UP &&
- (avctx->codec->update_thread_context || !THREAD_SAFE_CALLBACKS(avctx))) {
+ (avctx->codec->update_thread_context
+#if FF_API_THREAD_SAFE_CALLBACKS
+ || !THREAD_SAFE_CALLBACKS(avctx)
+#endif
+ )) {
+FF_ENABLE_DEPRECATION_WARNINGS
av_log(avctx, AV_LOG_ERROR, "get_buffer() cannot be called after ff_thread_finish_setup()\n");
return -1;
}
@@ -938,6 +981,10 @@ static int thread_get_buffer_internal(AVCodecContext *avctx, ThreadFrame *f, int
}
pthread_mutex_lock(&p->parent->buffer_mutex);
+#if !FF_API_THREAD_SAFE_CALLBACKS
+ err = ff_get_buffer(avctx, f->f, flags);
+#else
+FF_DISABLE_DEPRECATION_WARNINGS
if (THREAD_SAFE_CALLBACKS(avctx)) {
err = ff_get_buffer(avctx, f->f, flags);
} else {
@@ -957,6 +1004,8 @@ static int thread_get_buffer_internal(AVCodecContext *avctx, ThreadFrame *f, int
}
if (!THREAD_SAFE_CALLBACKS(avctx) && !avctx->codec->update_thread_context)
ff_thread_finish_setup(avctx);
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
if (err)
av_buffer_unref(&f->progress);
@@ -965,6 +1014,8 @@ static int thread_get_buffer_internal(AVCodecContext *avctx, ThreadFrame *f, int
return err;
}
+#if FF_API_THREAD_SAFE_CALLBACKS
+FF_DISABLE_DEPRECATION_WARNINGS
enum AVPixelFormat ff_thread_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt)
{
enum AVPixelFormat res;
@@ -990,6 +1041,8 @@ enum AVPixelFormat ff_thread_get_format(AVCodecContext *avctx, const enum AVPixe
return res;
}
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
int ff_thread_get_buffer(AVCodecContext *avctx, ThreadFrame *f, int flags)
{
@@ -1001,12 +1054,16 @@ int ff_thread_get_buffer(AVCodecContext *avctx, ThreadFrame *f, int flags)
void ff_thread_release_buffer(AVCodecContext *avctx, ThreadFrame *f)
{
+#if FF_API_THREAD_SAFE_CALLBACKS
+FF_DISABLE_DEPRECATION_WARNINGS
PerThreadContext *p = avctx->internal->thread_ctx;
FrameThreadContext *fctx;
AVFrame *dst;
int ret = 0;
int can_direct_free = !(avctx->active_thread_type & FF_THREAD_FRAME) ||
THREAD_SAFE_CALLBACKS(avctx);
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
if (!f->f)
return;
@@ -1017,6 +1074,9 @@ void ff_thread_release_buffer(AVCodecContext *avctx, ThreadFrame *f)
av_buffer_unref(&f->progress);
f->owner[0] = f->owner[1] = NULL;
+#if !FF_API_THREAD_SAFE_CALLBACKS
+ av_frame_unref(f->f);
+#else
// when the frame buffers are not allocated, just reset it to clean state
if (can_direct_free || !f->f->buf[0]) {
av_frame_unref(f->f);
@@ -1058,4 +1118,5 @@ fail:
memset(f->f->extended_buf, 0, f->f->nb_extended_buf * sizeof(*f->f->extended_buf));
av_frame_unref(f->f);
}
+#endif
}
diff --git a/libavcodec/thread.h b/libavcodec/thread.h
index 540135fbc9..9361d481f6 100644
--- a/libavcodec/thread.h
+++ b/libavcodec/thread.h
@@ -96,6 +96,7 @@ void ff_thread_report_progress(ThreadFrame *f, int progress, int field);
*/
void ff_thread_await_progress(ThreadFrame *f, int progress, int field);
+#if FF_API_THREAD_SAFE_CALLBACKS
/**
* Wrapper around get_format() for frame-multithreaded codecs.
* Call this function instead of avctx->get_format().
@@ -105,6 +106,9 @@ void ff_thread_await_progress(ThreadFrame *f, int progress, int field);
* @param fmt The list of available formats.
*/
enum AVPixelFormat ff_thread_get_format(AVCodecContext *avctx, const enum AVPixelFormat *fmt);
+#else
+#define ff_thread_get_format ff_get_format
+#endif
/**
* Wrapper around get_buffer() for frame-multithreaded codecs.
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 3255679550..10d5e552c2 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -673,6 +673,19 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *code
goto free_and_end;
}
+#if FF_API_THREAD_SAFE_CALLBACKS
+FF_DISABLE_DEPRECATION_WARNINGS
+ if ((avctx->thread_type & FF_THREAD_FRAME) &&
+ avctx->get_buffer2 != avcodec_default_get_buffer2 &&
+ !avctx->thread_safe_callbacks) {
+ av_log(avctx, AV_LOG_WARNING, "Requested frame threading with a "
+ "custom get_buffer2() implementation which is not marked as "
+ "thread safe. This is not supported anymore, make your "
+ "callback thread-safe.\n");
+ }
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
+
avctx->codec = codec;
if ((avctx->codec_type == AVMEDIA_TYPE_UNKNOWN || avctx->codec_type == codec->type) &&
avctx->codec_id == AV_CODEC_ID_NONE) {
diff --git a/libavcodec/version.h b/libavcodec/version.h
index 9fc637313d..5b4dfea579 100644
--- a/libavcodec/version.h
+++ b/libavcodec/version.h
@@ -144,6 +144,9 @@
#ifndef FF_API_UNUSED_CODEC_CAPS
#define FF_API_UNUSED_CODEC_CAPS (LIBAVCODEC_VERSION_MAJOR < 59)
#endif
+#ifndef FF_API_THREAD_SAFE_CALLBACKS
+#define FF_API_THREAD_SAFE_CALLBACKS (LIBAVCODEC_VERSION_MAJOR < 59)
+#endif
#endif /* AVCODEC_VERSION_H */
--
2.27.0
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