[lttng-dev] Tracepoints firing without being enabled in LTTng

Tue Feb 19 16:37:00 EST 2019

Hello,

Sorry for the late reply. I was able to figure out the weird behavior from
the application. Turns out if I run my application as a service,  lttng no
longer can see any of the UST tracepoints and causes the behavior I was
explaining.
When I execute the application normally (./app_name), the functionality is
as expected. Is this the expected behavior? Is there some way I can trace
the userspace application while running it as a service simultaneously?

Thanks for any info,
Mosleh

On Fri, Feb 15, 2019 at 2:48 PM Francis Deslauriers <
francis.deslauriers at efficios.com> wrote:

> Can you start the lttng-sessiond in verbose mode using the following
> command:
> > lttng-sessiond -vvv
> and then do the lttng create, start of application and lttng view on
> another console.
>
> Then copy the output of the sessiond on https://pastebin.com/ and send us
> the link.
>
> Thank you,
> Francis
>
> Le ven. 15 févr. 2019, à 14 h 36, Mosleh Uddin <mosleh1235 at gmail.com> a
> écrit :
>
>> That's correct, I don't enable any events or do: lttng start.
>> Here is some snapshots of starting everything up, followed by starting my
>> application.
>> [image: image.png]
>>
>> Here are the outputs for the commands:
>>
>> [image: image.png]
>>
>> [image: image.png]
>>
>> [image: image.png]
>>
>> Note that even though the session is inactive, when a trace event occurs
>> in my application it is being recorded in the appropriate directory:
>>
>> [image: image.png]
>>
>> Also maybe important, the system has root only user. Would having the
>> application belonging to a different user and trying to run as root cause
>> these kinds of complications? I did notice when testing on a raspberry pi
>> that running an application as a root user would mean running sessions as
>> root user as well.
>>
>> Thanks,
>> Mosleh
>>
>> On Fri, Feb 15, 2019 at 11:55 AM Francis Deslauriers <
>> francis.deslauriers at efficios.com> wrote:
>>
>>> Adding back lttng-dev mailing list.
>>>
>>> So you don't even run a lttng-enable-event command?
>>> That's odd.
>>>
>>> Can you send us the output of the following commands:
>>> Is it possible that there are other lttng-sessiond daemons running on
>>> the machine?
>>> > ps aux | grep "lttng-sessiond"
>>> Verify if there are other active tracing sessions:
>>> > lttng list
>>> Check the details of the current session:
>>> > lttng status
>>>
>>> Thank you,
>>> Francis
>>>
>>> Le ven. 15 févr. 2019, à 11 h 29, Mosleh Uddin <mosleh1235 at gmail.com> a
>>> écrit :
>>> >
>>> > Hi Francis,
>>> >
>>> > Thank you for the quick response.
>>> > Just to clear things up, my application is running when I run that
>>> command.
>>> >
>>> > The commands I am running are:
>>> > > lttng-sessiond -d
>>> > > lttng create my-sess --live
>>> > After this command I start my application. If I then do the command:
>>> > > lttng view
>>> > I will see the tracepoints in the application in the terminal even
>>> though I have not done: lttng start.
>>> >
>>> > I thought it was strange that I cannot find my application in the:
>>> lttng list command under any domain.
>>> > Also the reason I start my application after creating a session is
>>> because the system automatically starts the application using systemd,
>>> > in order to get tracing data at all I have to manually stop the
>>> application and start it again after creating a session.
>>> >
>>> > Thanks again for any help,
>>> > Mosleh
>>> >
>>> > On Fri, Feb 15, 2019 at 10:32 AM Francis Deslauriers <
>>> francis.deslauriers at efficios.com> wrote:
>>> >>
>>> >> Hi Mosleh,
>>> >> It's expected to not see any event when running lttng list -u if no
>>> >> lttng-ust instrumented applications are running.
>>> >>
>>> >> What are the exact lttng commands you are running to see those
>>> >> unexpected events?
>>> >>
>>> >> Thank you,
>>> >> Francis
>>> >>
>>> >>
>>> >> Le ven. 15 févr. 2019, à 10 h 08, Mosleh Uddin <mosleh1235 at gmail.com>
>>> a écrit :
>>> >> >
>>> >> > Hello,
>>> >> >
>>> >> > I am having a strange issue with my current application. For some
>>> context, I have integrated LTTng into a Yocto build and put custom trace
>>> points in my embedded system application. Once I load the built image onto
>>> my system and start a session daemon, I try to list all available userspace
>>> events (using lttng list -u), but no events show up.
>>> >> >
>>> >> > The strange occurrence is when I create a session (lltng create
>>> my-sess) and not start tracing the trace events will display on the screen
>>> regardless (when starting session in live mode with lttng view). I was
>>> wondering if anyone has any insight on this issue I am having.
>>> >> >
>>> >> > Thanks for any assistance,
>>> >> > Mosleh
>>> >> > _______________________________________________
>>> >> > lttng-dev mailing list
>>> >> > lttng-dev at lists.lttng.org
>>> >> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>> >>
>>> >> --
>>> >> Francis Deslauriers
>>> >> Computer Engineer
>>> >> EfficiOS inc.
>>>
>>>
>>>
>>> --
>>> Francis Deslauriers
>>> Computer Engineer
>>> EfficiOS inc.
>>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>
>
> --
> Francis Deslauriers
> Computer Engineer
> EfficiOS inc.
>
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