Re: [lttng-dev] I'm still getting empty ust traces using tracef - Michael Jeanson via lttng-dev

From: Michael Jeanson via lttng-dev <lttng-dev@lists.lttng.org>
To: lttng-dev@lists.lttng.org
Subject: Re: [lttng-dev] I'm still getting empty ust traces using tracef
Date: Thu, 11 May 2023 14:14:31 -0400	[thread overview]
Message-ID: <6ffecb5c-fa2f-9ace-bc50-5b5f49f36d42@efficios.com> (raw)
In-Reply-To: <CAFZh4h8awEpJgAcygRY=1f7A2qK91b31HBnLBPvvueuRnquOjQ@mail.gmail.com>

On 2023-05-11 12:36, Brian Hutchinson via lttng-dev wrote:
> ... more background.  I've always used ltt in the kernel so I don't
> have much experience with the user side of it and especially
> multi-threaded, multi-core so I'm probably missing some fundamental
> concepts that I need to understand.
> 
> Regards,
> 
> Brian

Hi,

If you are static linking 'liblttng-ust' then the library constructor won't be 
executed and you'll get no traces. While this setup is untested and 
unsupported, you could call the UST constructor from your application early 
initialisation but that would require patching lttng-ust to export the 
'lttng_ust_ctor' symbol.

And the first thing to do to start diagnosing UST tracing issues is to run 
your application with hte LTTNG_UST_DEBUG environment variable set, see [1] 
for details.

Cheers,

Michael

[1] https://lttng.org/man/3/lttng-ust/v2.13/#doc-_environment_variables

_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev