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

[Mathieu Desnoyers]

----- On Feb 12, 2016, at 12:02 PM, Mathieu Desnoyers <mathieu.desnoyers at efficios.com> wrote: 

> ---- On Feb 11, 2016, at 9:01 AM, Sean Heelan <seanheelan at gmail.com> wrote:

>> 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!

> It appears that sem_timedwait() returns an unexpected error.

> Can you add a ERROR("sem_timedwait"); just before the assert at line 1582 in
> your liblttng-ust/lttng-ust-comm.c
> and show us the output ?

> Also, what is the value of your LTTNG_UST_REGISTER_TIMEOUT env. var. ?

Also, what architecture, Linux distribution, and kernel 
version are you using ? 

Thanks, 

Mathieu 

> Thanks,

> Mathieu

>> Sean

>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
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> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com

> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
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-- 
Mathieu Desnoyers 
EfficiOS Inc. 
http://www.efficios.com 
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