[FFmpeg-devel] [PATCH 1/2] pthreads: Fix bug introduced with thread_safe_callbacks

[Ronald S. Bultje]

Hi,

On Mon, Feb 28, 2011 at 4:34 PM, Alexander Strange
<astrange at ithinksw.com> wrote:
>
> On Feb 17, 2011, at 3:43 PM, Ronald S. Bultje wrote:
>
>> Hi,
>>
>> On Thu, Feb 17, 2011 at 4:10 AM, Alexander Strange
>> <astrange at ithinksw.com> wrote:
>>> For intra codecs, ff_thread_finish_setup() is called before decoding starts
>>> automatically. However, get_buffer can only be used before it's called, so
>>> adding this requirement broke frame threading for them. Fixed by moving the
>>> call until after get_buffer is finished.
>>> ---
>>> ?libavcodec/pthread.c | ? ?8 ++++++--
>>> ?1 files changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/libavcodec/pthread.c b/libavcodec/pthread.c
>>> index 0e033d3..096b371 100644
>>> --- a/libavcodec/pthread.c
>>> +++ b/libavcodec/pthread.c
>>> @@ -292,7 +292,8 @@ static attribute_align_arg void *frame_worker_thread(void *arg)
>>>
>>> ? ? ? ? if (fctx->die) break;
>>>
>>> - ? ? ? ?if (!codec->update_thread_context) ff_thread_finish_setup(avctx);
>>> + ? ? ? ?if (!codec->update_thread_context && !avctx->thread_safe_callbacks)
>>> + ? ? ? ? ? ?ff_thread_finish_setup(avctx);
>>>
>>> ? ? ? ? pthread_mutex_lock(&p->mutex);
>>> ? ? ? ? avcodec_get_frame_defaults(&p->frame);
>>> @@ -779,7 +780,7 @@ int ff_thread_get_buffer(AVCodecContext *avctx, AVFrame *f)
>>> ? ? ? ? return avctx->get_buffer(avctx, f);
>>> ? ? }
>>>
>>> - ? ?if (p->state != STATE_SETTING_UP) {
>>> + ? ?if (p->state != STATE_SETTING_UP && avctx->codec->update_thread_context) {
>>> ? ? ? ? av_log(avctx, AV_LOG_ERROR, "get_buffer() cannot be called after ff_thread_finish_setup()\n");
>>> ? ? ? ? return -1;
>>> ? ? }
>>> @@ -810,6 +811,9 @@ int ff_thread_get_buffer(AVCodecContext *avctx, AVFrame *f)
>>> ? ? ? ? err = p->result;
>>>
>>> ? ? ? ? pthread_mutex_unlock(&p->progress_mutex);
>>> +
>>> + ? ? ? ?if (!avctx->codec->update_thread_context)
>>> + ? ? ? ? ? ?ff_thread_finish_setup(avctx);
>>> ? ? }
>>>
>>> ? ? pthread_mutex_unlock(&p->parent->buffer_mutex);
>>> --
>>> 1.7.4.1
>>
>> Does this mean in some situations ff_thread_finish_setup will be called twice?
>
> No, but there was a deadlock bug in the first line...
>
> Also made the error condition in the second chunk more complex.
> (p->state != STATE_SETTING_UP && !avctx->thread_safe_callbacks) will never happen in current code, but it's the kind of bug that's easy to introduce with an unrelated change.
>
> Reattached both patches here.

Current version looks OK to me, I'll leave it for a few hours for
others to comment and then apply.

Ronald