[FFmpeg-devel] [PATCH v3 1/3] lavc/utils.c: use C11 atomics for entangled thread handling

[Rostislav Pehlivanov]

On 25 November 2017 at 18:37, James Almer <jamrial at gmail.com> wrote:

> On 11/25/2017 2:01 PM, Rostislav Pehlivanov wrote:
> > Signed-off-by: Rostislav Pehlivanov <atomnuker at gmail.com>
> > ---
> >  libavcodec/utils.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> > index e50de6e89b..3a0f3c11f5 100644
> > --- a/libavcodec/utils.c
> > +++ b/libavcodec/utils.c
> > @@ -56,6 +56,7 @@
> >  #include "version.h"
> >  #include <stdlib.h>
> >  #include <stdarg.h>
> > +#include <stdatomic.h>
> >  #include <limits.h>
> >  #include <float.h>
> >  #if CONFIG_ICONV
> > @@ -114,7 +115,7 @@ static int (*lockmgr_cb)(void **mutex, enum AVLockOp
> op) = NULL;
> >
> >
> >  volatile int ff_avcodec_locked;
> > -static int volatile entangled_thread_counter = 0;
> > +static atomic_int entangled_thread_counter = ATOMIC_VAR_INIT(0);
> >  static void *codec_mutex;
> >  static void *avformat_mutex;
> >
> > @@ -1944,11 +1945,11 @@ int ff_lock_avcodec(AVCodecContext *log_ctx,
> const AVCodec *codec)
> >              return -1;
> >      }
> >
> > -    if (avpriv_atomic_int_add_and_fetch(&entangled_thread_counter, 1)
> != 1) {
> > +    if (atomic_fetch_add(&entangled_thread_counter, 1)) {
> >          av_log(log_ctx, AV_LOG_ERROR,
> >                 "Insufficient thread locking. At least %d threads are "
> >                 "calling avcodec_open2() at the same time right now.\n",
> > -               entangled_thread_counter);
> > +               atomic_load(&entangled_thread_counter));
> >          if (!lockmgr_cb)
> >              av_log(log_ctx, AV_LOG_ERROR, "No lock manager is set,
> please see av_lockmgr_register()\n");
> >          ff_avcodec_locked = 1;
> > @@ -1967,7 +1968,7 @@ int ff_unlock_avcodec(const AVCodec *codec)
> >
> >      av_assert0(ff_avcodec_locked);
> >      ff_avcodec_locked = 0;
> > -    avpriv_atomic_int_add_and_fetch(&entangled_thread_counter, -1);
> > +    atomic_fetch_add(&entangled_thread_counter, -1);
>
> Nit: You could use atomic_fetch_sub() instead of adding -1.
>
> >      if (lockmgr_cb) {
> >          if ((*lockmgr_cb)(&codec_mutex, AV_LOCK_RELEASE))
> >              return -1;
> >
>
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>

Fixed locally