[lttng-dev] Crash on first run of target using liblttng-ust-cyg-profile.so, but subsequent runs succeed

[Sean Heelan]

Hi all,

I am running a target within a Docker instance, and tracing function
execution using the latest LTTng release (2.7). The commands I am issuing
look as follows:

----
lttng create cc_session -o bla
lttng enable-event --userspace lttng_ust_cyg_profile:func_entry
lttng start

LD_PRELOAD=liblttng-ust-cyg-profile.so target

lttng stop
lttng destroy
----

When the target is executed it aborts with the following error:

----
php: lttng-ust-comm.c:1582: lttng_ust_init: Assertion `!ret' failed.
----

If I rerun the command it then works fine. In fact, simply doing the
following within the Docker container demonstrates the issue:

----
LD_PRELOAD=liblttng-ust-cyg-profile.so ls
LD_PRELOAD=liblttng-ust-cyg-profile.so ls
----

The first 'ls' will fail at the same point mentioned above, while the
second will succeed. Off the top of my head I'm struggling to come up with
an explanation as to what impact the first execution using LD_PRELOAD would
have on the second. Does it impact a shared lib cache in some way, which
I'm unaware of?

Any assistance would be appreciated!

Sean
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