Re: [Qemu-devel] [RFC PATCH v3 4/5] Update documentation for LTTng ust tracing

[Mohamad Gebai <mohamad.gebai@polymtl.ca>]

On 13-10-17 05:20 AM, Alex Bennée wrote:
> mohamad.gebai@polymtl.ca writes:
>
>> On 13-10-16 08:05 AM, Alex Bennée wrote:
>>>>> Running this gives me:
>>>>>
>>>>> <quote>
>>>>> UST events:
>>>>> -------------
>>>>> None
>>>>> </quote>
>>>>>
>>>>> Before or after running qemu. What is the mechanism lttng expects to
>>>>> find out all these events?
>>>> Either the user should belong the group "tracing", or launch the
>>>> lttng-sessiond daemon (lttng-sessiond -d).
>>> <snip>
>>>
>>> Hmm I've done both and I get nothing still. I can enable all tracepoints
>>> though. This could just be a Ubuntu weirdness thing though.
>> That's weird. I did test it on a clean Ubuntu Precise (in a VM) and I
>> didn't have any problem after either one of these steps. Can you please
>> make sure that the user belongs to the "tracing" group and that the
>> lttng-sessiond daemon is running before running any instance of Qemu.
>> Also, Qemu should be running for LTTng to be able to list the events.
> Ahh that was it. I suggest you change the wording from:
>
> "Package lttng-tools is required for userspace tracing. After running Qemu, LTTng
> should be able to list all available events:"
>
> to
>
> "Package lttng-tools is required for userspace tracing. While running
> and instrumented Qemu, LTTng should be able to list all available events:"

Oops! Sorry about that.
>
>> Does lttng enable-event -a -u/start/stop/view show any event?
> Yes, as I said the rest worked fine. With that minor wording fix I'm happy.
>
> Thanks for getting this back into shape :-)
>
Happy to do it, I hope it will be useful to others.

Mohamad