[FFmpeg-devel] [PATCH 3/3 v2] avfilter: use a mutex instead of atomics in avfilter_register()

[James Almer]

On 1/5/2018 1:04 PM, wm4 wrote:
> On Thu,  4 Jan 2018 22:42:52 -0300
> James Almer <jamrial at gmail.com> wrote:
> 
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  libavfilter/avfilter.c | 15 +++++++++++----
>>  1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
>> index b98b32bacb..ff7df672fd 100644
>> --- a/libavfilter/avfilter.c
>> +++ b/libavfilter/avfilter.c
>> @@ -19,7 +19,6 @@
>>   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>>   */
>>  
>> -#include "libavutil/atomic.h"
>>  #include "libavutil/avassert.h"
>>  #include "libavutil/avstring.h"
>>  #include "libavutil/buffer.h"
>> @@ -33,6 +32,7 @@
>>  #include "libavutil/pixdesc.h"
>>  #include "libavutil/rational.h"
>>  #include "libavutil/samplefmt.h"
>> +#include "libavutil/thread.h"
>>  
>>  #define FF_INTERNAL_FIELDS 1
>>  #include "framequeue.h"
>> @@ -590,19 +590,26 @@ const AVFilter *avfilter_get_by_name(const char *name)
>>      return NULL;
>>  }
>>  
>> +static AVMutex filter_register_mutex = AV_MUTEX_INITIALIZER;
>> +
>>  int avfilter_register(AVFilter *filter)
>>  {
>> -    AVFilter **f = last_filter;
>> +    AVFilter **f;
>>  
>>      /* the filter must select generic or internal exclusively */
>>      av_assert0((filter->flags & AVFILTER_FLAG_SUPPORT_TIMELINE) != AVFILTER_FLAG_SUPPORT_TIMELINE);
>>  
>> -    filter->next = NULL;
>> +    ff_mutex_lock(&filter_register_mutex);
>> +    f = last_filter;
>>  
>> -    while(*f || avpriv_atomic_ptr_cas((void * volatile *)f, NULL, filter))
>> +    while (*f)
>>          f = &(*f)->next;
>> +    *f = filter;
>> +    filter->next = NULL;
>>      last_filter = &filter->next;
>>  
>> +    ff_mutex_unlock(&filter_register_mutex);
>> +
>>      return 0;
>>  }
>>  
> 
> Also seems good.

Pushed.