--- st_cb_syncobj.c.orig	2016-10-14 10:52:02.867414704 +0900
+++ st_cb_syncobj.c	2016-10-18 01:31:48.477581393 +0900
@@ -36,21 +36,25 @@
 #include "pipe/p_screen.h"
 #include "st_context.h"
 #include "st_cb_syncobj.h"
+#include <pthread.h>
 
 struct st_sync_object {
    struct gl_sync_object b;
-
    struct pipe_fence_handle *fence;
+   mtx_t mtx;
 };
 
 
 static struct gl_sync_object * st_new_sync_object(struct gl_context *ctx,
                                                   GLenum type)
 {
-   if (type == GL_SYNC_FENCE)
-      return (struct gl_sync_object*)CALLOC_STRUCT(st_sync_object);
-   else
-      return NULL;
+   if (type == GL_SYNC_FENCE) {
+      struct st_sync_object * so = 
+         (struct st_sync_object*)CALLOC_STRUCT(st_sync_object);
+      mtx_init(&so->mtx, mtx_plain);
+      return (struct gl_sync_object *)so;
+   }
+   return NULL;
 }
 
 static void st_delete_sync_object(struct gl_context *ctx,
@@ -61,6 +65,7 @@
 
    screen->fence_reference(screen, &so->fence, NULL);
    free(so->b.Label);
+   mtx_destroy(&so->mtx);
    free(so);
 }
 
@@ -82,15 +87,12 @@
    struct st_sync_object *so = (struct st_sync_object*)obj;
 
    /* If the fence doesn't exist, assume it's signalled. */
-   if (!so->fence) {
-      so->b.StatusFlag = GL_TRUE;
-      return;
-   }
-
-   if (screen->fence_finish(screen, so->fence, 0)) {
+   mtx_lock(&so->mtx);
+   if (so->fence && screen->fence_finish(screen, so->fence, 0)) {
       screen->fence_reference(screen, &so->fence, NULL);
       so->b.StatusFlag = GL_TRUE;
    }
+   mtx_unlock(&so->mtx);
 }
 
 static void st_client_wait_sync(struct gl_context *ctx,
@@ -100,20 +102,15 @@
    struct pipe_screen *screen = st_context(ctx)->pipe->screen;
    struct st_sync_object *so = (struct st_sync_object*)obj;
 
-   /* If the fence doesn't exist, assume it's signalled. */
-   if (!so->fence) {
-      so->b.StatusFlag = GL_TRUE;
-      return;
-   }
-
    /* We don't care about GL_SYNC_FLUSH_COMMANDS_BIT, because flush is
     * already called when creating a fence. */
-
-   if (so->fence &&
-       screen->fence_finish(screen, so->fence, timeout)) {
+   mtx_lock(&so->mtx);
+   /* If the fence doesn't exist, assume it's signalled. */
+   if (so->fence && screen->fence_finish(screen, so->fence, timeout)) {
       screen->fence_reference(screen, &so->fence, NULL);
       so->b.StatusFlag = GL_TRUE;
    }
+   mtx_unlock(&so->mtx);
 }
 
 static void st_server_wait_sync(struct gl_context *ctx,