[vlc-devel] [PATCH] DxVA2: lock the buffer pool when getting/releasing a buffer

[Rémi Denis-Courmont]

Le 2015-04-02 16:33, Steve Lhomme a écrit :
> in frame threading mode, the buffers can be requested from different
> threads, resulting in a race condition
>
> Doesn't fix #11693
> ---
>  modules/codec/avcodec/dxva2.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/modules/codec/avcodec/dxva2.c 
> b/modules/codec/avcodec/dxva2.c
> index f4289ee..76a1ebb 100644
> --- a/modules/codec/avcodec/dxva2.c
> +++ b/modules/codec/avcodec/dxva2.c
> @@ -265,6 +265,7 @@ typedef struct {
>      LPDIRECT3DSURFACE9 d3d;
>      int                refcount;
>      unsigned int       order;
> +    vlc_va_sys_t       *sys;
>  } vlc_va_surface_t;
>
>  #define VA_DXVA2_MAX_SURFACE_COUNT (64)
> @@ -274,6 +275,8 @@ struct vlc_va_sys_t
>      int          width;
>      int          height;
>
> +    vlc_mutex_t     surface_lock;
> +
>      /* DLL */
>      HINSTANCE             hd3d9_dll;
>      HINSTANCE             hdxva2_dll;
> @@ -468,6 +471,8 @@ static int Get(vlc_va_t *va, void **opaque,
> uint8_t **data)
>          return VLC_EGENERIC;
>      }
>
> +    vlc_mutex_lock( &sys->surface_lock );
> +
>      /* Grab an unused surface, in case none are, try the oldest
>       * XXX using the oldest is a workaround in case a problem
> happens with libavcodec */
>      unsigned i, old;
> @@ -489,6 +494,9 @@ static int Get(vlc_va_t *va, void **opaque,
> uint8_t **data)
>      surface->order = sys->surface_order++;
>      *data = (void *)surface->d3d;
>      *opaque = surface;
> +
> +    vlc_mutex_unlock( &sys->surface_lock );
> +
>      return VLC_SUCCESS;
>  }
>
> @@ -496,8 +504,12 @@ static void Release(void *opaque, uint8_t *data)
>  {
>      vlc_va_surface_t *surface = opaque;
>
> +    vlc_mutex_lock( &surface->sys->surface_lock );
> +
>      surface->refcount--;
>      (void) data;
> +
> +    vlc_mutex_unlock( &surface->sys->surface_lock );

This could use atomic or interlocked operations.

>  }
>
>  static void Close(vlc_va_t *va, AVCodecContext *ctx)
> @@ -515,6 +527,7 @@ static void Close(vlc_va_t *va, AVCodecContext 
> *ctx)
>          FreeLibrary(sys->hdxva2_dll);
>      if (sys->hd3d9_dll)
>          FreeLibrary(sys->hd3d9_dll);
> +    vlc_mutex_destroy( &sys->surface_lock );
>
>      free((char *)va->description);
>      free(sys);
> @@ -530,6 +543,8 @@ static int Open(vlc_va_t *va, AVCodecContext
> *ctx, const es_format_t *fmt)
>      sys->codec_id = ctx->codec_id;
>      (void) fmt;
>
> +    vlc_mutex_init( &sys->surface_lock );
> +
>      /* Load dll*/
>      sys->hd3d9_dll = LoadLibrary(TEXT("D3D9.DLL"));
>      if (!sys->hd3d9_dll) {
> @@ -927,6 +942,7 @@ static int DxCreateVideoDecoder(vlc_va_t *va,
>          surface->d3d = sys->hw_surface[i];
>          surface->refcount = 0;
>          surface->order = 0;
> +        surface->sys = sys;
>      }
>      msg_Dbg(va, "IDirectXVideoAccelerationService_CreateSurface
> succeed with %d surfaces (%dx%d)",
>              sys->surface_count, fmt->i_width, fmt->i_height);

-- 
Rémi Denis-Courmont