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


From: Mohamad Gebai
Subject: Re: [Qemu-devel] [RFC PATCH v3 4/5] Update documentation for LTTng ust tracing
Date: Fri, 18 Oct 2013 02:38:43 -0400
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6

On 13-10-17 05:20 AM, Alex Bennée wrote:
address@hidden 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



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