linux-kernel - Re: [tip:perf/x86] perf, x86: Implement initial P4 PMU driver

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Date:	Tue, 16 Mar 2010 19:23:14 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Robert Richter <robert.richter@....com>
Cc:	mingo@...hat.com, hpa@...or.com, acme@...hat.com,
	eranian@...gle.com, linux-kernel@...r.kernel.org,
	peterz@...radead.org, fweisbec@...il.com, ming.m.lin@...el.com,
	tglx@...utronix.de, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:perf/x86] perf, x86: Implement initial P4 PMU driver

On Tue, Mar 16, 2010 at 05:07:33PM +0100, Robert Richter wrote:
[...]
> --
> 
> From: Robert Richter <robert.richter@....com>
> Date: Tue, 16 Mar 2010 16:38:19 +0100
> Subject: [PATCH] perf, x86: reporting error code that returns from x86_pmu.hw_config()
> 
> If x86_pmu.hw_config() fails a fixed error code (-EOPNOTSUPP) is
> return even if a different error was reported. This patch fixes this.
> 
> Signed-off-by: Robert Richter <robert.richter@....com>
> ---
>  arch/x86/kernel/cpu/perf_event.c |    5 +++--
>  1 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
> index 4e2480f..8982d92 100644
> --- a/arch/x86/kernel/cpu/perf_event.c
> +++ b/arch/x86/kernel/cpu/perf_event.c
> @@ -467,8 +467,9 @@ static int __hw_perf_event_init(struct perf_event *event)
>  	hwc->last_tag = ~0ULL;
>  
>  	/* Processor specifics */
> -	if (x86_pmu.hw_config(attr, hwc))
> -		return -EOPNOTSUPP;
> +	err = x86_pmu.hw_config(attr, hwc);
> +	if (err)
> +		return err;
>  
>  	if (!hwc->sample_period) {
>  		hwc->sample_period = x86_pmu.max_period;
> -- 
> 1.7.0
>

Though at moment all hw_config callees return 0, it's better
to be ready if one day we may start returning some particular
errors. Looks good to me. Objections?

	-- Cyrill
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