[vlc-devel] [PATCH] DXVA2: lock the buffer pool when getting/releasing a buffer (v3)

[Steve Lhomme]

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

--
replaces the previous patches 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..27abf22 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_mutex_t        *p_lock;
 } 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;
@@ -487,15 +494,24 @@ 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;
 }
 
 static void Release(void *opaque, uint8_t *data)
 {
     vlc_va_surface_t *surface = opaque;
+    if ( surface->p_lock )
+        vlc_mutex_lock( surface->p_lock );
 
     surface->refcount--;
     (void) data;
+
+    if ( surface->p_lock )
+        vlc_mutex_unlock( surface->p_lock );
 }
 
 static void Close(vlc_va_t *va, AVCodecContext *ctx)
@@ -513,6 +529,8 @@ 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 +546,10 @@ 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 +958,8 @@ static int DxCreateVideoDecoder(vlc_va_t *va, int codec_id,
         surface->d3d = sys->hw_surface[i];
         surface->refcount = 0;
         surface->order = 0;
+        if ( sys->b_thread_safe )
+            surface->p_lock = &sys->surface_lock;
     }
     msg_Dbg(va, "IDirectXVideoAccelerationService_CreateSurface succeed with %d surfaces (%dx%d)",
             sys->surface_count, fmt->i_width, fmt->i_height);
-- 
2.3.2