On Mon, 2013-04-08 at 07:50 -0700, Linus Torvalds wrote:
> ---
> diff --git a/include/linux/preempt.h b/include/linux/preempt.h
> index 5a710b9c578e..465df1c13386 100644
> --- a/include/linux/preempt.h
> +++ b/include/linux/preempt.h
> @@ -93,14 +93,17 @@ do { \
>
> #else /* !CONFIG_PREEMPT_COUNT */
>
> -#define preempt_disable() do { } while (0)
> -#define sched_preempt_enable_no_resched() do { } while (0)
> -#define preempt_enable_no_resched() do { } while (0)
> -#define preempt_enable() do { } while (0)
> -
> -#define preempt_disable_notrace() do { } while (0)
> -#define preempt_enable_no_resched_notrace() do { } while (0)
> -#define preempt_enable_notrace() do { } while (0)
> +/* This is only a barrier to other asms. Notably get_user/put_user */
Probably should add in the comment:
" or anything else that can cause a hidden schedule. "
-- Steve
> +#define asm_barrier() asm volatile("")
> +
> +#define preempt_disable() asm_barrier()
> +#define sched_preempt_enable_no_resched() asm_barrier()
> +#define preempt_enable_no_resched() asm_barrier()
> +#define preempt_enable() asm_barrier()
> +
> +#define preempt_disable_notrace() asm_barrier()
> +#define preempt_enable_no_resched_notrace() asm_barrier()
> +#define preempt_enable_notrace() asm_barrier()
>
> #endif /* CONFIG_PREEMPT_COUNT */
--
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