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

From: Ingo Molnar
Date: Thu Oct 03 2013 - 08:38:28 EST



* Ramkumar Ramachandra <artagnon@xxxxxxxxx> 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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