[Mesa-dev] [PATCH v2] i965: don't require 64bit cmpxchg

[Matt Turner]

On Sun, Mar 5, 2017 at 1:23 PM, Grazvydas Ignotas <notasas at gmail.com> wrote:
> There are still some distributions trying to support unfortunate people
> with old or exotic CPUs that don't have 64bit atomic operations. The
> only thing preventing compile of the Intel driver for them seems to be
> initialization of a debug variable.
>
> v2: use call_once() instead of unsafe code, as suggested by Matt Turner
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93089
> Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
> ---
> no commit access
>
>  src/intel/common/gen_debug.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/src/intel/common/gen_debug.c b/src/intel/common/gen_debug.c
> index 858f04d..96efdab 100644
> --- a/src/intel/common/gen_debug.c
> +++ b/src/intel/common/gen_debug.c
> @@ -33,8 +33,8 @@
>
>  #include "common/gen_debug.h"
>  #include "util/macros.h"
> -#include "util/u_atomic.h" /* for p_atomic_cmpxchg */
>  #include "util/debug.h"
> +#include "c11/threads.h"
>
>  uint64_t INTEL_DEBUG = 0;
>
> @@ -101,9 +101,17 @@ intel_debug_flag_for_shader_stage(gl_shader_stage stage)
>     return flags[stage];
>  }
>
> +static void
> +brw_process_intel_debug_variable_once(void)
> +{
> +   INTEL_DEBUG = parse_debug_string(getenv("INTEL_DEBUG"), debug_control);
> +}
> +
>  void
>  brw_process_intel_debug_variable(void)
>  {
> -   uint64_t intel_debug = parse_debug_string(getenv("INTEL_DEBUG"), debug_control);
> -   (void) p_atomic_cmpxchg(&INTEL_DEBUG, 0, intel_debug);
> +   static once_flag process_intel_debug_variable_flag = ONCE_FLAG_INIT;
> +
> +   call_once(&process_intel_debug_variable_flag,
> +             brw_process_intel_debug_variable_once);
>  }

Thank you. That looks great.

Reviewed-by: Matt Turner <mattst88 at gmail.com>

I'll commit it tomorrow morning, if there are no further comments.