On Sun, 2010-01-24 at 18:36 -0800, Igor Oliveira wrote:
> The patch fixes the bug 25863.
> The bug happens when i use blend types like multiply, screen, dark in
> vega state tracker.
>
> --- a/src/gallium/drivers/softpipe/sp_state_sampler.c
> +++ b/src/gallium/drivers/softpipe/sp_state_sampler.c
> @@ -244,7 +244,7 @@ softpipe_reset_sampler_varients(struct
> softpipe_context *softpipe)
> * fragment programs.
> */
> for (i = 0; i <= softpipe->vs->max_sampler; i++) {
> - if (softpipe->vertex_samplers[i]) {
> + if (softpipe->vertex_samplers[i] && softpipe->vertex_textures[i]) {
> softpipe->tgsi.vert_samplers_list[i] =
> get_sampler_varient( i,
> sp_sampler(softpipe->vertex_samplers[i]),
> @@ -258,7 +258,7 @@ softpipe_reset_sampler_varients(struct
> softpipe_context *softpipe)
> }
>
> for (i = 0; i <= softpipe->fs->info.file_max[TGSI_FILE_SAMPLER]; i++) {
> - if (softpipe->sampler[i]) {
> + if (softpipe->sampler[i] && softpipe->texture[i]) {
> softpipe->tgsi.frag_samplers_list[i] =
> get_sampler_varient( i,
> sp_sampler(softpipe->sampler[i]),
> --
> 1.6.3.3
This doesn't seem the best way to fix this: the segfault may happen in
softpipe code, but the state tracker has the responsibility to sanitize
state. Shouldn't the vega state tracker bind a dummy black texture in
this case?
Also, the net effect of this patch is to use the previously bound
texture/sampler -- which may be null -- so the bug is potentially still
there, but perhaps less likely.
I wonder why changing blend type causes a null texture to be bound in
the first place? I recall from Zack's VG talk that certain kind of
blending ops had to be implemented with texturing, but binding a null
texture binding seems a symptom of some subtle bug.
Jose
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