Re: [PATCH v5 4/9] perf/x86: Add compiler barrier after updating BTS

[Leo Yan]

Hi Peter, or any x86 maintainer,

On Mon, Aug 09, 2021 at 07:14:02PM +0800, Leo Yan wrote:
> Since BTS is coherent, simply add a compiler barrier to separate the BTS
> update and aux_head store.

Could you reivew this patch and check if BTS needs the comipler
barrier in this case?  Thanks.

> Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx>
> ---
>  arch/x86/events/intel/bts.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
> index 6320d2cfd9d3..974e917e65b2 100644
> --- a/arch/x86/events/intel/bts.c
> +++ b/arch/x86/events/intel/bts.c
> @@ -209,6 +209,12 @@ static void bts_update(struct bts_ctx *bts)
>  	} else {
>  		local_set(&buf->data_size, head);
>  	}
> +
> +	/*
> +	 * Since BTS is coherent, just add compiler barrier to ensure
> +	 * BTS updating is ordered against bts::handle::event.
> +	 */
> +	barrier();
>  }
>  
>  static int
> -- 
> 2.25.1
>