Re: [PATCH V7 1/8] perf,tools: introduce generic FEAT for CPU attributes

[Jiri Olsa <jolsa@redhat.com>]

On Fri, Aug 28, 2015 at 05:48:02AM -0400, Kan Liang wrote:

SNIP

>  
> +static int process_cpu_attributes(struct perf_file_section *section __maybe_unused,
> +				  struct perf_header *ph, int fd,
> +				  void *data __maybe_unused)
> +{
> +	ssize_t ret;
> +	u32 i, tag_id;
> +	u64 nr;
> +
> +	for (i = 0; i < PERF_HEADER_CPU_ATTR_MAX; i++) {
> +
> +		ret = readn(fd, &tag_id, sizeof(tag_id));
> +		if (ret != sizeof(tag_id))
> +			return -1;
> +
> +		if (ph->needs_swap)
> +			nr = bswap_32(tag_id);
> +
> +		if (tag_id >= PERF_HEADER_CPU_ATTR_MAX) {
> +			pr_debug("The number of cpu attributes is not expected. "
> +				 "You may need to upgrade the perf tool.\n");
> +			return -1;
> +		}

I wonder we should let it pass to be able to read new data
with older perf.. but IMO the error is specific enough to
find & fix it if it ever happens

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka