[Mesa-dev] [PATCHv2 04/13] glsl: protect anonymous struct id with a mutex

[Ian Romanick]

On 07/09/2014 12:47 AM, Chia-I Wu wrote:
> There may be two contexts compiling shaders at the same time, and we want the
> anonymous struct id to be globally unique.
> 
> Signed-off-by: Chia-I Wu <olv at lunarg.com>
> ---
>  src/glsl/glsl_parser_extras.cpp | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/src/glsl/glsl_parser_extras.cpp b/src/glsl/glsl_parser_extras.cpp
> index b327c2b..ad31469 100644
> --- a/src/glsl/glsl_parser_extras.cpp
> +++ b/src/glsl/glsl_parser_extras.cpp
> @@ -1347,9 +1347,15 @@ ast_struct_specifier::ast_struct_specifier(const char *identifier,
>  					   ast_declarator_list *declarator_list)
>  {
>     if (identifier == NULL) {
> +      static mtx_t mutex = _MTX_INITIALIZER_NP;
>        static unsigned anon_count = 1;
> -      identifier = ralloc_asprintf(this, "#anon_struct_%04x", anon_count);
> -      anon_count++;
> +      unsigned count;
> +
> +      mtx_lock(&mutex);
> +      count = anon_count++;
> +      mtx_unlock(&mutex);

My previous feedback on this was to try and use some sort of atomic
counter when available.  I'm not excited about the performance hit of
taking a lock here.  Although, this probably isn't hit too much.  After
this lands, can you submit an enhancement bug for this issue?

> +
> +      identifier = ralloc_asprintf(this, "#anon_struct_%04x", count);
>     }
>     name = identifier;
>     this->declarations.push_degenerate_list_at_head(&declarator_list->link);
>