Date: Mon, 31 Aug 2015 11:46:38 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Kan Liang <kan.liang@intel.com>
Cc: acme@kernel.org, jolsa@kernel.org, a.p.zijlstra@chello.nl, luto@kernel.org,
        mingo@redhat.com, eranian@google.com, ak@linux.intel.com,
        mark.rutland@arm.com, adrian.hunter@intel.com, namhyung@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH V7 1/8] perf,tools: introduce generic FEAT for CPU
 attributes
Message-ID: <20150831094638.GF22039@krava.brq.redhat.com>
References: <1440755289-30939-1-git-send-email-kan.liang@intel.com>
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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
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