[lttng-dev] Problem with vpid in lttng output

[Jonathan Rajotte-Julien]

Hi Aleksander,

On Mon, Sep 02, 2019 at 12:01:46PM +0000, Aleksander Twardowski via lttng-dev wrote:
> Hi,
> 
> I do not know if I am addressing problem correctly but let’s try 😊
> I have a problem, occurring very rarely, with vpid in lttng output.
> Sometimes, I do not know why, vpid is not visible.
> 
> Proper lttng log:
> [14:08:35.156333670] (+0.000010724) selilsx1795 com_ericsson_csim_up:ERROR: { cpu_id = 0 }, { vpid = 16826 }, { src = "/home/ealetwa/repos/bpu-up/src/Rpup.cpp:125:", obj = "GENERAL", msg = "Failed to initialize SDS connection" }

Side note: make sure to redact information that could be sensitive. Here the
payload and event name could be considered sensitive. It is up to you to
evaluate what is sensitive and what is not.

> 
> Problematic lttng log:
> “[14:08:35.156333670] (+0.000010724) selilsx1795 com_ericsson_csim_up:ERROR: { cpu_id = 0 }, { src = "/home/ealetwa/repos/bpu-up/src/Rpup.cpp:125:", obj = "GENERAL", msg = "Failed to initialize SDS connection" }”

Does this situation happen inside the same trace? Or does it seems to happens
between traces?

> 
> If you can help me, tell me in which cases this problem occurring that would be great.

We are not aware of any ongoing issue with the context subsystem. A first step
would be to validate that the "lttng add-context" (or equivalent) was performed
without any error for the session of the trace with the vpid information
missing. Note that you cannot add context field for a tracing session if it was
started at least once.

Cheers

-- 
Jonathan Rajotte-Julien
EfficiOS