avcodec/parser: use a mutex instead of atomics in av_register_codec_parser()

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>

libavcodec/parser.c

@@ -25,9 +25,9 @@
 #include <string.h>
 
 #include "libavutil/avassert.h"
-#include "libavutil/atomic.h"
 #include "libavutil/internal.h"
 #include "libavutil/mem.h"
+#include "libavutil/thread.h"
 
 #include "internal.h"
 #include "parser.h"
@@ -42,11 +42,14 @@ AVCodecParser *av_parser_next(const AVCodecParser *p)
         return av_first_parser;
 }
 
+static AVMutex parser_register_mutex = AV_MUTEX_INITIALIZER;
+
 void av_register_codec_parser(AVCodecParser *parser)
 {
-    do {
-        parser->next = av_first_parser;
-    } while (parser->next != avpriv_atomic_ptr_cas((void * volatile *)&av_first_parser, parser->next, parser));
+    ff_mutex_lock(&parser_register_mutex);
+    parser->next = av_first_parser;
+    av_first_parser = parser;
+    ff_mutex_unlock(&parser_register_mutex);
 }
 
 AVCodecParserContext *av_parser_init(int codec_id)