[Mesa-dev] [PATCH] i965/gen6: Fix crash with VS+TF after rendering with GS

[Tapani Pälli]

Reviewed-by: Tapani Pälli <tapani.palli at intel.com>

On 01/07/2015 11:08 AM, Iago Toral Quiroga wrote:
> Rendering with a GS and then using transform feedback with a program that does
> not have a GS can crash in gen6. The reason for this is that
> brw_begin_transform_feedback checks brw->geometry_program to decide if there
> is a GS program, but this is not correct: brw->geometry_program is updated when
> issuing drawing commands, so after rendering with a GS it will be non-NULL
> until we draw again with a program that does not have a GS. If the next
> program uses TF, we will call glBegintransformFeedback before issuing
> the drawing command and hence brw->geometry_program will be non-NULL if
> the previous rendering used a GS. The right thing to do here is to check
> ctx->_Shader->CurrentProgram[MESA_SHADER_GEOMETRY] instead. This is what the
> gen7 code path does too.
>
> Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=87694
> ---
>   src/mesa/drivers/dri/i965/gen6_sol.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/gen6_sol.c b/src/mesa/drivers/dri/i965/gen6_sol.c
> index 0dafd0f..ff93de3 100644
> --- a/src/mesa/drivers/dri/i965/gen6_sol.c
> +++ b/src/mesa/drivers/dri/i965/gen6_sol.c
> @@ -241,7 +241,7 @@ brw_begin_transform_feedback(struct gl_context *ctx, GLenum mode,
>
>      assert(brw->gen == 6);
>
> -   if (brw->geometry_program) {
> +   if (ctx->_Shader->CurrentProgram[MESA_SHADER_GEOMETRY]) {
>         /* BRW_NEW_GEOMETRY_PROGRAM */
>         shaderprog =
>            ctx->_Shader->CurrentProgram[MESA_SHADER_GEOMETRY];
>