linux-kernel - Re: [PATCH] perf tools: Clarify error when running "perf lock record"

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Date:	Thu, 05 Sep 2013 08:29:10 -0600
From:	David Ahern <dsahern@...il.com>
To:	Rodrigo Campos <rodrigo@...g.com.ar>
CC:	linux-kernel@...r.kernel.org, a.p.zijlstra@...llo.nl,
	paulus@...ba.org, mingo@...hat.com, acme@...stprotocols.net,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] perf tools: Clarify error when running "perf lock record"

On 9/5/13 2:32 AM, Rodrigo Campos wrote:
> If you have the config options enabled in your kernel, you still need to be root
> to run perf lock. And is kind of misleading when you have that options enabled
> and the error says that they might not be.
>
> So, this patch just adds to the error that it should be run as root. Although we
> can probably check if it's running as root or not, adding it to the error
> message is really simple and should be enough.
>
> Signed-off-by: Rodrigo Campos <rodrigo@...g.com.ar>
> ---
> Please keep me in Cc: since I'm not subscribed
> ---
>   tools/perf/builtin-lock.c |    4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/builtin-lock.c b/tools/perf/builtin-lock.c
> index 76543a4..f07b318 100644
> --- a/tools/perf/builtin-lock.c
> +++ b/tools/perf/builtin-lock.c
> @@ -886,8 +886,8 @@ static int __cmd_record(int argc, const char **argv)
>   	for (i = 0; i < ARRAY_SIZE(lock_tracepoints); i++) {
>   		if (!is_valid_tracepoint(lock_tracepoints[i].name)) {
>   				pr_err("tracepoint %s is not enabled. "
> -				       "Are CONFIG_LOCKDEP and CONFIG_LOCK_STAT enabled?\n",
> -				       lock_tracepoints[i].name);
> +				       "Are CONFIG_LOCKDEP and CONFIG_LOCK_STAT enabled "
> +				       "and running as root?\n", lock_tracepoints[i].name);
>   				return 1;
>   		}
>   	}
>

you can run perf-lock as non-root with certain settings. It would be 
better to discriminate debugfs access errors (insufficient privilege). 
That means improving is_valid_tracepoint and handling the errors in 
perf-lock.

David
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