[FFmpeg-devel] [PATCH] [Trac ticket #3194] libavcodec/utils: Statically initialize global mutexes to avoid a leak.

[Hendrik Leppkes]

On Sun, Dec 15, 2013 at 1:10 PM, wm4 <nfxjfg at googlemail.com> wrote:
> On Sun, 15 Dec 2013 12:59:58 +0100
> Hendrik Leppkes <h.leppkes at gmail.com> wrote:
>
>> On Sun, Dec 15, 2013 at 12:17 PM, Tomer Barletz <barletz at gmail.com> wrote:
>> > ---
>> >  libavcodec/utils.c | 25 +++++++------------------
>> >  1 file changed, 7 insertions(+), 18 deletions(-)
>> >
>> > diff --git a/libavcodec/utils.c b/libavcodec/utils.c
>> > index 73370fe..0653acc 100644
>> > --- a/libavcodec/utils.c
>> > +++ b/libavcodec/utils.c
>> > @@ -74,20 +74,6 @@ static int default_lockmgr_cb(void **arg, enum AVLockOp op)
>> >      case AV_LOCK_CREATE:
>> >          return 0;
>> >      case AV_LOCK_OBTAIN:
>> > -        if (!*mutex) {
>> > -            pthread_mutex_t *tmp = av_malloc(sizeof(pthread_mutex_t));
>> > -            if (!tmp)
>> > -                return AVERROR(ENOMEM);
>> > -            if ((err = pthread_mutex_init(tmp, NULL))) {
>> > -                av_free(tmp);
>> > -                return AVERROR(err);
>> > -            }
>> > -            if (avpriv_atomic_ptr_cas(mutex, NULL, tmp)) {
>> > -                pthread_mutex_destroy(tmp);
>> > -                av_free(tmp);
>> > -            }
>> > -        }
>> > -
>> >          if ((err = pthread_mutex_lock(*mutex)))
>> >              return AVERROR(err);
>> >
>> > @@ -100,8 +86,7 @@ static int default_lockmgr_cb(void **arg, enum AVLockOp op)
>> >      case AV_LOCK_DESTROY:
>> >          if (*mutex)
>> >              pthread_mutex_destroy(*mutex);
>> > -        av_free(*mutex);
>> > -        avpriv_atomic_ptr_cas(mutex, *mutex, NULL);
>> > +
>> >          return 0;
>> >      }
>> >      return 1;
>> > @@ -114,8 +99,12 @@ static int (*lockmgr_cb)(void **mutex, enum AVLockOp op) = NULL;
>> >
>> >  volatile int ff_avcodec_locked;
>> >  static int volatile entangled_thread_counter = 0;
>> > -static void *codec_mutex;
>> > -static void *avformat_mutex;
>> > +
>> > +static pthread_mutex_t codec_mutex_real = PTHREAD_MUTEX_INITIALIZER;
>> > +static void *codec_mutex = &codec_mutex_real;
>> > +
>> > +static pthread_mutex_t avformat_mutex_real = PTHREAD_MUTEX_INITIALIZER;
>> > +static void *avformat_mutex = &avformat_mutex_real;
>> >
>> >  #if FF_API_FAST_MALLOC && CONFIG_SHARED && HAVE_SYMVER
>> >  FF_SYMVER(void*, av_fast_realloc, (void *ptr, unsigned int *size, size_t min_size), "LIBAVCODEC_55")
>>
>> Static initialization doesn't work with the w32threads compat wrapper,
>> and as such, this patch would break this use-case.
>
> So why doesn't libavcodec use one of the pthread implementations for
> windows?

It can, but it also can use native win32 threads.
The only complaint is lack of static initializers, no reason to force
pthreads just for that.