linux-kernel - Re: [PATCH V4 07/14] perf/x86/intel: Support hardware TopDown metrics

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Message-ID: <20190930133624.GO4553@hirez.programming.kicks-ass.net>
Date:   Mon, 30 Sep 2019 15:36:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     kan.liang@...ux.intel.com
Cc:     acme@...nel.org, mingo@...hat.com, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, jolsa@...nel.org, eranian@...gle.com,
        alexander.shishkin@...ux.intel.com, ak@...ux.intel.com
Subject: Re: [PATCH V4 07/14] perf/x86/intel: Support hardware TopDown metrics

On Mon, Sep 16, 2019 at 06:41:21AM -0700, kan.liang@...ux.intel.com wrote:
> +static int add_nr_metric_event(struct cpu_hw_events *cpuc,
> +			       struct perf_event *event,
> +			       int *max_count)
> +{
> +	/* There are 4 TopDown metrics events. */
> +	if (is_metric_event(event) && (++cpuc->n_metric_event > 4))
> +		return -EINVAL;
> +
> +	*max_count += cpuc->n_metric_event;

That's busted; it would increment with 1,2,3,4 for a total of 10.

> +
> +	return 0;
> +}