[Mesa-dev] [PATCH] st/dri: Remove useless flush front.

[Jose Fonseca]

Stephane,

Although flushing the front buffer may be unnecessary, flushing itself is not, as glXMakeCurrent mandates that the current must be flushed:

   "Pending commands to the previous context, if any, are flushed before it is released."

So this flush call can only be removed, if a flush is done elsewhere in DRI shared code, otherwise rendering queued in that context may not happen.

Jose

----- Original Message -----
> In the following scenario:
> - CreateContext C1
> - MakeCurrent C1
> - DestroyContext C1 (does not actually destroy the first context,
> postponed
>   until the next MakeCurrent)
> - CreateContext C2
> - MakeCurrent C2
> 
> MakeCurrent will call flush on a context which might not even have
> had a front
> buffer, leading to crashes. Since none of the dri drivers use the
> flush in
> their unbind_context implementation either, we remove this useless
> flush front
> call.
> 
> This fixes GPU crashes with Chrome and gallium drivers.
> ---
>  .../state_trackers/dri/common/dri_context.c        |    1 -
>  1 files changed, 0 insertions(+), 1 deletions(-)
> 
> diff --git a/src/gallium/state_trackers/dri/common/dri_context.c
> b/src/gallium/state_trackers/dri/common/dri_context.c
> index b47d8d9..226c630 100644
> --- a/src/gallium/state_trackers/dri/common/dri_context.c
> +++ b/src/gallium/state_trackers/dri/common/dri_context.c
> @@ -188,7 +188,6 @@ dri_unbind_context(__DRIcontext * cPriv)
>  
>     if (--ctx->bind_count == 0) {
>        if (ctx->st == ctx->stapi->get_current(ctx->stapi)) {
> -         ctx->st->flush(ctx->st, ST_FLUSH_FRONT, NULL);
>           stapi->make_current(stapi, NULL, NULL, NULL);
>        }
>     }
> --
> 1.7.5.3.367.ga9930
> 
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