[vlc-devel] [PATCH] DXVA2: lock the buffer pool when getting/releasing a buffer

[Steve Lhomme]

On Fri, Apr 3, 2015 at 1:12 PM, Steve Lhomme <robUx4 at videolabs.io> wrote:
> in frame threading mode, the buffers can be requested from different threads, resulting in a race condition
> only needed if thread_safe_callbacks is set in avcodec

The same thing might be needed in VAAPI as well.

> --
> replaces the previous patch with the same name
> ---
>  modules/codec/avcodec/dxva2.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
>
> diff --git a/modules/codec/avcodec/dxva2.c b/modules/codec/avcodec/dxva2.c
> index 3f3707e..e3941ca 100644
> --- a/modules/codec/avcodec/dxva2.c
> +++ b/modules/codec/avcodec/dxva2.c
> @@ -263,6 +263,7 @@ 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)
> @@ -272,6 +273,9 @@ struct vlc_va_sys_t
>      int          width;
>      int          height;
>
> +    bool            b_thread_safe;
> +    vlc_mutex_t     surface_lock;
> +
>      /* DLL */
>      HINSTANCE             hd3d9_dll;
>      HINSTANCE             hdxva2_dll;
> @@ -466,6 +470,9 @@ static int Get(vlc_va_t *va, void **opaque, uint8_t **data)
>          return VLC_EGENERIC;
>      }
>
> +    if ( sys->b_thread_safe )
> +        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;
> @@ -487,6 +494,10 @@ static int Get(vlc_va_t *va, void **opaque, uint8_t **data)
>      surface->order = sys->surface_order++;
>      *data = (void *)surface->d3d;
>      *opaque = surface;
> +
> +    if ( sys->b_thread_safe )
> +        vlc_mutex_unlock( &sys->surface_lock );
> +
>      return VLC_SUCCESS;
>  }
>
> @@ -494,8 +505,14 @@ static void Release(void *opaque, uint8_t *data)
>  {
>      vlc_va_surface_t *surface = opaque;
>
> +    if ( surface->sys->b_thread_safe )
> +        vlc_mutex_lock( &surface->sys->surface_lock );
> +
>      surface->refcount--;
>      (void) data;
> +
> +    if ( surface->sys->b_thread_safe )
> +        vlc_mutex_unlock( &surface->sys->surface_lock );
>  }
>
>  static void Close(vlc_va_t *va, AVCodecContext *ctx)
> @@ -513,6 +530,8 @@ static void Close(vlc_va_t *va, AVCodecContext *ctx)
>          FreeLibrary(sys->hdxva2_dll);
>      if (sys->hd3d9_dll)
>          FreeLibrary(sys->hd3d9_dll);
> +    if ( sys->b_thread_safe )
> +        vlc_mutex_destroy( &sys->surface_lock );
>
>      free((char *)va->description);
>      free(sys);
> @@ -528,6 +547,10 @@ static int Open(vlc_va_t *va, AVCodecContext *ctx, const es_format_t *fmt)
>      sys->codec_id = ctx->codec_id;
>      (void) fmt;
>
> +    sys->b_thread_safe = ctx->thread_safe_callbacks;
> +    if ( sys->b_thread_safe )
> +        vlc_mutex_init( &sys->surface_lock );
> +
>      /* Load dll*/
>      sys->hd3d9_dll = LoadLibrary(TEXT("D3D9.DLL"));
>      if (!sys->hd3d9_dll) {
> @@ -936,6 +959,7 @@ static int DxCreateVideoDecoder(vlc_va_t *va, int codec_id,
>          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);
> --
> 2.3.2
>
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