linux-kernel - Re: [PATCH v9 3.2 7/9] tracing: uprobes trace

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Date:	Tue, 17 Jan 2012 13:11:59 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-mm <linux-mm@...ck.org>, Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Roland McGrath <roland@...k.frob.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Anton Arapov <anton@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v9 3.2 7/9] tracing: uprobes trace_event interface


A couple of 'perf probe' usability issues.

When running it as unprivileged user right now it fails with:

 $ perf probe -x /lib64/libc.so.6 free
 Failed to open uprobe_events file: Permission denied

That error message should reference the full file name in 
question, i.e. /sys/kernel/debug/tracing/uprobe_events - that 
way the user can make that file writable if it's secure to do 
that on that system.

The other thing is the text that gets printed:

 $ perf probe --del free
 Remove event: probe_libc:free

that's not how tools generally communicate - it should be 
something like:

 $ perf probe --del free
 Removed event: probe_libc:free

Note the past tense - this tells the user that the action has 
been performed successfully.

Likewise, 'perf probe --add' should talk in past tense as well, 
to indicate success. So it should say something like:

 $ perf probe -x /lib64/libc.so.6 free
 Added new event:
  probe_libc:free      (on 0x7f080)

 You can now use it in all perf tools, such as:

	perf record -e probe_libc:free -aR sleep 1

(Also note the s/on/in change in the other text.)

Thanks,

	Ingo
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