3 files changed, 46 insertions, 5 deletions

diff --git a/src/mesa/main/arrayobj.c b/src/mesa/main/arrayobj.c
index cf9c5d7ecc7..2526404fda3 100644
--- a/src/mesa/main/arrayobj.c
+++ b/src/mesa/main/arrayobj.c
@@ -53,6 +53,7 @@
 #include "varray.h"
 #include "main/dispatch.h"
 #include "util/bitscan.h"
+#include "util/u_atomic.h"
 
 
 const GLubyte
@@ -331,10 +332,16 @@ _mesa_reference_vao_(struct gl_context *ctx,
       /* Unreference the old array object */
       struct gl_vertex_array_object *oldObj = *ptr;
 
-      assert(oldObj->RefCount > 0);
-      oldObj->RefCount--;
+      bool deleteFlag;
+      if (oldObj->SharedAndImmutable) {
+         deleteFlag = p_atomic_dec_zero(&oldObj->RefCount);
+      } else {
+         assert(oldObj->RefCount > 0);
+         oldObj->RefCount--;
+         deleteFlag = (oldObj->RefCount == 0);
+      }
 
-      if (oldObj->RefCount == 0)
+      if (deleteFlag)
          _mesa_delete_vao(ctx, oldObj);
 
       *ptr = NULL;
@@ -343,9 +350,13 @@ _mesa_reference_vao_(struct gl_context *ctx,
 
    if (vao) {
       /* reference new array object */
-      assert(vao->RefCount > 0);
+      if (vao->SharedAndImmutable) {
+         p_atomic_inc(&vao->RefCount);
+      } else {
+         assert(vao->RefCount > 0);
+         vao->RefCount++;
+      }
 
-      vao->RefCount++;
       *ptr = vao;
    }
 }
@@ -407,6 +418,7 @@ _mesa_initialize_vao(struct gl_context *ctx,
    vao->Name = name;
 
    vao->RefCount = 1;
+   vao->SharedAndImmutable = false;
 
    /* Init the individual arrays */
    for (i = 0; i < ARRAY_SIZE(vao->VertexAttrib); i++) {
@@ -452,6 +464,9 @@ _mesa_update_vao_derived_arrays(struct gl_context *ctx,
 {
    GLbitfield arrays = vao->NewArrays;
 
+   /* Make sure we do not run into problems with shared objects */
+   assert(!vao->SharedAndImmutable || vao->NewArrays == 0);
+
    while (arrays) {
       const int attrib = u_bit_scan(&arrays);
       struct gl_vertex_array *array = &vao->_VertexArray[attrib];
@@ -465,6 +480,16 @@ _mesa_update_vao_derived_arrays(struct gl_context *ctx,
 }
 
 
+void
+_mesa_set_vao_immutable(struct gl_context *ctx,
+                        struct gl_vertex_array_object *vao)
+{
+   _mesa_update_vao_derived_arrays(ctx, vao);
+   vao->NewArrays = 0;
+   vao->SharedAndImmutable = true;
+}
+
+
 bool
 _mesa_all_varyings_in_vbos(const struct gl_vertex_array_object *vao)
 {
diff --git a/src/mesa/main/arrayobj.h b/src/mesa/main/arrayobj.h
index 5de74505bb8..8da5c9ffe01 100644
--- a/src/mesa/main/arrayobj.h
+++ b/src/mesa/main/arrayobj.h
@@ -81,6 +81,15 @@ extern void
 _mesa_update_vao_derived_arrays(struct gl_context *ctx,
                                 struct gl_vertex_array_object *vao);
 
+
+/**
+ * Mark the vao as shared and immutable, do remaining updates.
+ */
+extern void
+_mesa_set_vao_immutable(struct gl_context *ctx,
+                        struct gl_vertex_array_object *vao);
+
+
 /* Returns true if all varying arrays reside in vbos */
 extern bool
 _mesa_all_varyings_in_vbos(const struct gl_vertex_array_object *vao);
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index bdecd422a9a..15f39cbacc3 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -1608,6 +1608,13 @@ struct gl_vertex_array_object
    GLboolean EverBound;
 
    /**
+    * Marked to true if the object is shared between contexts and immutable.
+    * Then reference counting is done using atomics and thread safe.
+    * Is used for dlist VAOs.
+    */
+   bool SharedAndImmutable;
+
+   /**
     * Derived vertex attribute arrays
     *
     * This is a legacy data structure created from gl_array_attributes and