linux-kernel - Re: [PATCH] perf tool: report user-friendly error from timechart

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Message-ID: <20131003123820.GA12004@gmail.com>
Date:	Thu, 3 Oct 2013 14:38:21 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Ramkumar Ramachandra <artagnon@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH] perf tool: report user-friendly error from timechart


* Ramkumar Ramachandra <artagnon@...il.com> wrote:

> +	/* Perform a quick sanity check */
> +	if (!is_valid_tracepoint("power:cpu_frequency")) {
> +		fprintf(stderr, "Error:\tNo permissions to read $debugfs/tracing/events/power/cpu_frequency\n");
> +		fprintf(stderr, "Hint:\tChange the permissions of debugfs: /sys/kernel/debug\n");
> +		fprintf(stderr, "\tThe directory will be present if your kernel was compiled with debugfs support.\n");

Is missing permissions the only way how is_valid_tracepoint() can fail?

What if debugfs has the right permissions but CONFIG_TRACEPOINTS is 
disabled in the kernel?

Thanks,

	Ingo
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