diff -crB intel-driver-1.0.18/src/gen6_mfd.c intel-driver-1.0.18_patch/src/gen6_mfd.c
*** intel-driver-1.0.18/src/gen6_mfd.c	Mon May 28 23:22:14 2012
--- intel-driver-1.0.18_patch/src/gen6_mfd.c	Thu Sep 27 13:11:27 2012
***************
*** 40,45 ****
--- 40,47 ----
  
  #include "gen6_mfd.h"
  
+ pthread_mutex_t free_avc_surface_lock;
+ 
  static const uint32_t zigzag_direct[64] = {
      0,   1,  8, 16,  9,  2,  3, 10,
      17, 24, 32, 25, 18, 11,  4,  5,
***************
*** 175,180 ****
--- 177,190 ----
      if (!gen6_avc_surface)
          return;
  
+      pthread_mutex_lock(&free_avc_surface_lock);
+     if (!gen6_avc_surface)
+     {
+       pthread_mutex_unlock(&free_avc_surface_lock);
+       return;
+     }
+ 
+ 
      dri_bo_unreference(gen6_avc_surface->dmv_top);
      gen6_avc_surface->dmv_top = NULL;
      dri_bo_unreference(gen6_avc_surface->dmv_bottom);
***************
*** 182,187 ****
--- 192,200 ----
  
      free(gen6_avc_surface);
      *data = NULL;
+ 
+     pthread_mutex_unlock(&free_avc_surface_lock);
+ 
  }
  
  static void