Subject: Re: [PATCH] perf_counter: more barrier in blank weak function

From: KOSAKI Motohiro <[email-masked]>
Date: Sat, 27 Dec 2008 15:07:06 +0900 (JST)

> 
> Impact: fix panic possible panic etc
> 
> some compiler seems to inline the weak global function if no line in it
> 
> Signed-off-by: Yinghai Lu <[email-masked]>
> 
> diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
> index d7a79f3..37f7716 100644
> --- a/kernel/perf_counter.c
> +++ b/kernel/perf_counter.c
> @@ -45,8 +45,8 @@ hw_perf_counter_init(struct perf_counter *counter)
>  }
>  
>  u64 __weak hw_perf_save_disable(void)		{ return 0; }
> -void __weak hw_perf_restore(u64 ctrl)		{ }
> -void __weak hw_perf_counter_setup(void)		{ }
> +void __weak hw_perf_restore(u64 ctrl)		{ barrier(); }
> +void __weak hw_perf_counter_setup(void)		{ barrier(); }

We need comment into the function.
I expect anyone think "hm, this barrier() is meaningless. let's cleanup." in the future.
we should avoid it.