[lttng-dev] Can't trace function calls

[Jonathan Rajotte-Julien]

Hi,

On Wed, Mar 31, 2021 at 10:51:03AM -0500, Ramesh Errabolu via lttng-dev wrote:
> I am trying to capture the list of functions being called by an app. The
> app relies on a couple of shared libraries (libhsa-runtime64.so and
> libhsakmt.so).

ok.

> 
> My experiments all *FAIL *i.e. there are no log files of the output.

Not sure what you mean here. But let's continue first. 

> The
> link on lttng-ust-cyg-profile does not tell me where I can get them.

Could you share the "link" in question?

> Instrument the build files for the two libraries to allow function tracing
> by the gcc/clang flags -finstrument-functions and run workload as follows
> 
>    - Instrument the build files for the two libraries to allow function
>    tracing by the gcc/clang flags *-finstrument-functions* and run workload
>    as follows

Okai. I expect that you have read this:
https://lttng.org/docs/v2.12/#doc-liblttng-ust-cyg-profile 

and this
https://lttng.org/man/3/lttng-ust-cyg-profile/v2.12/

> I am using LTTng version Ubuntu: LTTng Stable 2.12 PPA
> 
>    - apt-get install lttng-tools
>    - apt-get install lttng-modules-dkms
>    - apt-get install liblttng-ust-dev
> 

Looks good.

> I noticed no kernel modules with substring "ltt" in it.

Okai so this is where we need much more information. 

First of all, what are the lttng commands used for your experiments? (lttng create, lttng enable-channel, lttng enable-event...) 
Please provide a sample script of your experiments. 

Second, you are mostly performing userspace tracing here, lttng-modules ( the
kernel tracer) might not even be needed here unless you also want to do kernel
tracing. 

What do you mean by "there are no log files of the output."? LTTng produces
traces encoded in CTF (Common Trace Format) that must be read by a reader
(Babeltrace most of the time).

Cheers

-- 
Jonathan Rajotte-Julien
EfficiOS