linux-kernel - Re: [PATCH v2 1/3] perf tool: fix reading new topology attribute "core

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Message-ID: <20200429181102.GE30487@kernel.org>
Date:   Wed, 29 Apr 2020 15:11:02 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>, Andi Kleen <ak@...ux.intel.com>,
        Dmitry Monakhov <dmtrmonakhov@...dex-team.ru>
Subject: Re: [PATCH v2 1/3] perf tool: fix reading new topology attribute
 "core_cpus"

Em Wed, Apr 29, 2020 at 07:19:47PM +0300, Konstantin Khlebnikov escreveu:
> Check access("devices/system/cpu/cpu%d/topology/core_cpus", F_OK) fails,
> unless current directory is "/sys". Simply try read this file first.
> 
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Fixes: 0ccdb8407a46 ("perf tools: Apply new CPU topology sysfs attributes")
> ---
>  tools/perf/util/smt.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)

Thanks, applied,

- Arnaldo
 
> diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
> index 3b791ef2cd50..8481842e9edb 100644
> --- a/tools/perf/util/smt.c
> +++ b/tools/perf/util/smt.c
> @@ -24,13 +24,13 @@ int smt_on(void)
>  
>  		snprintf(fn, sizeof fn,
>  			"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
> -		if (access(fn, F_OK) == -1) {
> +		if (sysfs__read_str(fn, &str, &strlen) < 0) {
>  			snprintf(fn, sizeof fn,
>  				"devices/system/cpu/cpu%d/topology/thread_siblings",
>  				cpu);
> +			if (sysfs__read_str(fn, &str, &strlen) < 0)
> +				continue;
>  		}
> -		if (sysfs__read_str(fn, &str, &strlen) < 0)
> -			continue;
>  		/* Entry is hex, but does not have 0x, so need custom parser */
>  		siblings = strtoull(str, NULL, 16);
>  		free(str);
> 

-- 

- Arnaldo