linux-kernel - Re: [PATCH 5/5] perf tools: Enhance parsing events tracepoint error output

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Date:	Fri, 11 Sep 2015 18:01:50 -0400
From:	Raphaël Beamonte <raphael.beamonte@...il.com>
To:	Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [PATCH 5/5] perf tools: Enhance parsing events tracepoint error output

2015-09-11 16:22 GMT-04:00 Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>:
> Em Fri, Sep 11, 2015 at 03:56:44PM -0400, Raphaël Beamonte escreveu:
>> Another possibility would be to have another perf command, sort of a
>> "perf remountfs", to run with sudo and that would make itself both
>> checks and remount accordingly the two fs.
>
> This part maybe more interesting, so I'll focus on it, yeah, having a:
> 'perf fixperms' command (have a better name? :) ) may make sense, would
> need context tho, i.e. something like:
>
>   perf fixperms trace
>
> Or:
>
>   perf fixperms top
>
> But then, perhaps in that case:
>
>   $ trace ls
>   Error:        No permissions to read
>   /sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit)
>   Hint: Try 'sudo mount -o remount,mode=755 /sys/kernel/debug'
>
> We could just add some more text saying that please check as well that
> the other parts of the path we're trying to access are available once
> the suggestion is followed.

Wouldn't it be almost the same as your "Something is wrong with
tracefs and/or debugfs, figure it out and try again" ? ;o)
I think that if the 'fixperms' need a context, we could as well give
the 'perf fixperms' command to type directly in the Hint, such as:

$ trace ls
Error:        No permissions to read
/sys/kernel/debug/tracing/events/raw_syscalls/sys_(enter|exit)
Hint: Try 'sudo perf fixperms trace'

It would be the same as the current copy/paste, but one command that
would fix the situation directly, instead of having to check the
permissions of each level in the path. A little bit user-friendlier!
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