linux-kernel - Re: [PATCH] tools/perf probe: Print a hint if adding a probe fails

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Date:   Mon, 21 Jun 2021 15:10:33 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tools/perf probe: Print a hint if adding a probe fails

Hi Arnaldo,

Arnaldo Carvalho de Melo wrote:
> Em Thu, Jun 10, 2021 at 07:29:26PM +0900, Masami Hiramatsu escreveu:
>> Hi Naveen,
>> 
>> On Thu, 10 Jun 2021 15:14:42 +0530
>> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
>> 
>> > Adding a probe can fail in a few scenarios. perf already checks for the
>> > address in the kprobe blacklist. However, the address could still be a
>> > jump label, or have a BUG_ON(). In such cases, it isn't always evident
>> > why adding the probe failed. Add a hint so that the user knows how to
>> > proceed.
>> > 
>> 
>> Thanks for the report.
>> 
>> Since now there is <tracefs>/error_log, if you see any errors in registering
>> probe-events, perf probe should dump the error_log for the hint message.
>> Also, kprobes should return the correct different error code for each
>> errors.
> 
> Was there any followup on this? I think we should do as Masami suggests,
> Naveen, could you do it?

Thanks for checking. We have been discussing this on the kernel side of 
things here (sorry, missed copying you on that):
http://lkml.kernel.org/r/20210610085617.1590138-1-naveen.n.rao@linux.vnet.ibm.com

I will work on the related changes to perf after the kernel changes.


Thanks,
Naveen