Re: [FFmpeg-devel] [PATCH 17/42] avcodec/refstruct: Add RefStruct pool API

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

Michael Niedermayer:
> On Tue, Sep 19, 2023 at 09:57:09PM +0200, Andreas Rheinhardt wrote:
>> Very similar to the AVBufferPool API, but with some differences:
>> 1. Reusing an already existing entry does not incur an allocation
>> at all any more (the AVBufferPool API needs to allocate an AVBufferRef).
>> 2. The tasks done while holding the lock are smaller; e.g.
>> allocating new entries is now performed without holding the lock.
>> The same goes for freeing.
>> 3. The entries are freed as soon as possible (the AVBufferPool API
>> frees them in two batches: The first in av_buffer_pool_uninit() and
>> the second immediately before the pool is freed when the last
>> outstanding entry is returned to the pool).
>> 4. The API is designed for objects and not naked buffers and
>> therefore has a reset callback. This is called whenever an object
>> is returned to the pool.
>> 5. Just like with the RefStruct API, custom allocators are not
>> supported.
>>
>> (If desired, the FFRefStructPool struct itself could be made
>> reference counted via the RefStruct API; an FFRefStructPool
>> would then be freed via ff_refstruct_unref().)
>>
>> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
>> ---
>>  libavcodec/refstruct.c | 194 ++++++++++++++++++++++++++++++++++++++++-
>>  libavcodec/refstruct.h | 128 +++++++++++++++++++++++++++
>>  2 files changed, 321 insertions(+), 1 deletion(-)
> 
> seems to break building on ppc (--disable-pthreads)
> 
> CC	libavcodec/refstruct.o
> src/libavcodec/refstruct.c: In function ‘pool_free’:
> src/libavcodec/refstruct.c:187:5: error: implicit declaration of function ‘pthread_mutex_destroy’; did you mean ‘ff_mutex_destroy’? [-Werror=implicit-function-declaration]
>      pthread_mutex_destroy(&pool->mutex);
>      ^~~~~~~~~~~~~~~~~~~~~
>      ff_mutex_destroy
> src/libavcodec/refstruct.c: In function ‘pool_return_entry’:
> src/libavcodec/refstruct.c:205:5: error: implicit declaration of function ‘pthread_mutex_lock’; did you mean ‘ff_mutex_lock’? [-Werror=implicit-function-declaration]
>      pthread_mutex_lock(&pool->mutex);
>      ^~~~~~~~~~~~~~~~~~
>      ff_mutex_lock
> src/libavcodec/refstruct.c:211:5: error: implicit declaration of function ‘pthread_mutex_unlock’; did you mean ‘ff_mutex_unlock’? [-Werror=implicit-function-declaration]
>      pthread_mutex_unlock(&pool->mutex);
>      ^~~~~~~~~~~~~~~~~~~~
>      ff_mutex_unlock
> src/libavcodec/refstruct.c: In function ‘ff_refstruct_pool_alloc_ext_c’:
> src/libavcodec/refstruct.c:339:11: error: implicit declaration of function ‘pthread_mutex_init’; did you mean ‘ff_mutex_init’? [-Werror=implicit-function-declaration]
>      err = pthread_mutex_init(&pool->mutex, NULL);
>            ^~~~~~~~~~~~~~~~~~
>            ff_mutex_init
> cc1: some warnings being treated as errors
> /home/michael/ffmpeg-git/ffmpeg/ffbuild/common.mak:81: recipe for target 'libavcodec/refstruct.o' failed
> make: *** [libavcodec/refstruct.o] Error 1
> make: Target 'all' not remade because of errors.

Sorry for not having tested --disable-pthreads. Will switch to our
ff_mutex-wrappers.

- Andreas

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