mesa: Enable true refcounting for NullBufferObj.

This object can be shared with another context, so we cannot just
delete it when the owning context is being destroyed.

Ensuring that buffer objects are properly refcounted guarantees
NullBufferObj is destroyed when all references to it are removed.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/mesa/main/pixel.c b/src/mesa/main/pixel.c
index f6f9c1173a1..ca6ecd7bfb6 100644
--- a/src/mesa/main/pixel.c
+++ b/src/mesa/main/pixel.c
@@ -150,13 +150,17 @@ validate_pbo_access(GLcontext *ctx, struct gl_pixelstore_attrib *pack,
    GLboolean ok;
 
    /* Note, need to use DefaultPacking and Unpack's buffer object */
-   ctx->DefaultPacking.BufferObj = pack->BufferObj;
+   _mesa_reference_buffer_object(ctx,
+                                 &ctx->DefaultPacking.BufferObj,
+                                 pack->BufferObj);
 
    ok = _mesa_validate_pbo_access(1, &ctx->DefaultPacking, mapsize, 1, 1,
                                   format, type, ptr);
 
    /* restore */
-   ctx->DefaultPacking.BufferObj = ctx->Shared->NullBufferObj;
+   _mesa_reference_buffer_object(ctx,
+                                 &ctx->DefaultPacking.BufferObj,
+                                 ctx->Shared->NullBufferObj);
 
    if (!ok) {
       _mesa_error(ctx, GL_INVALID_OPERATION,