On Tue, Mar 7, 2017 at 1:44 PM, wm4 <nfx...@googlemail.com> wrote:
> On Tue, 7 Mar 2017 02:47:36 +0700
> Muhammad Faiz <mfc...@gmail.com> wrote:
>
>> Signed-off-by: Muhammad Faiz <mfc...@gmail.com>
>> ---
>> libavcodec/allcodecs.c | 13 ++++++++++---
>> 1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/libavcodec/allcodecs.c b/libavcodec/allcodecs.c
>> index eee322b..1d05fc1 100644
>> --- a/libavcodec/allcodecs.c
>> +++ b/libavcodec/allcodecs.c
>> @@ -24,6 +24,8 @@
>> * Provide registration of all codecs, parsers and bitstream filters for
>> libavcodec.
>> */
>>
>> +#include <stdatomic.h>
>> +
>> #include "config.h"
>> #include "avcodec.h"
>> #include "version.h"
>> @@ -60,11 +62,14 @@
>>
>> void avcodec_register_all(void)
>> {
>> - static int initialized;
>> + static atomic_int initialized;
>> + static atomic_int ready;
>>
>> - if (initialized)
>> + if (atomic_exchange_explicit(&initialized, 1, memory_order_relaxed)) {
>> + while (!atomic_load_explicit(&ready, memory_order_relaxed))
>> + ;
>> return;
>> - initialized = 1;
>> + }
>>
>> /* hardware accelerators */
>> REGISTER_HWACCEL(H263_VAAPI, h263_vaapi);
>> @@ -716,4 +721,6 @@ void avcodec_register_all(void)
>> REGISTER_PARSER(VP8, vp8);
>> REGISTER_PARSER(VP9, vp9);
>> REGISTER_PARSER(XMA, xma);
>> +
>> + atomic_store_explicit(&ready, 1, memory_order_relaxed);
>> }
>
> avcodec_register() is already "safe" by attempting to do lock-free and
> wait-free list insertion (not very convincing IMHO, but it's there).
> Should that code be removed? Does anyone know why avcodec_register() is
> even still public API? The same affects some other things.
I don't know about these.
>
> Also, if you want to do it right, please use ff_thread_once() to do it
> without busy waiting. It works like pthread_once(), which was invented
> to avoid such constructions.
Ok, thank's for the suggestion
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