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Date: Tue, 17 Jan 2012 13:11:59 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>, Arnaldo Carvalho de Melo <acme@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
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        Arnaldo Carvalho de Melo <acme@infradead.org>,
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        Jim Keniston <jkenisto@linux.vnet.ibm.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH v9 3.2 7/9] tracing: uprobes trace_event interface
Message-ID: <20120117121159.GA4959@elte.hu>
References: <20120110114821.17610.9188.sendpatchset@srdronam.in.ibm.com>
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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