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

KOSAKI Motohiro
2008-12-27T06:07:26Z

>
> 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 <yinghai@kernel.org>
>
> 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.