[ltt-dev] lockdep trace

[Alexandre Montplaisir]

On 11-03-16 10:34 AM, Mathieu Desnoyers wrote:
> * Harald Gustafsson (hgu1972 at gmail.com) wrote:
>>> Sounds good. Which version of lttng are you using ?
>> I have tried this both on my x86 machine using the ubuntu ppa package
>> which uses kernel 2.6.35-24 and to me unknown lttng version. But I
>> also tried this on a ARM development board with kernel 2.6.34 and
>> lttng version 0.221 without success.
>>
>>> In your kernel config, under the "Kernel Hacking" menu, did you enable
>>> the options related to lock dependency debug, and lock proving and so
>>> on ? You should ensure that CONFIG_LOCKDEP is selected in your kernel
>>> config file.
>> In the ubuntu-ppa lttng package only LOCKDEP_SUPPORT is enabled, not
>> LOCKDEP and not LOCKDEP_DEBUG, neither DEBUG_LOCK_ALLOC,
>> PROVE_LOCKING, LOCK_STAT or any of the
>> INLINE_{READ|WRITE|SPIN}_LOCK_*. The same configuration have been used
>> on the ARM board.
>>
>> Hence, I should enable LOCKDEP, LOCKDEP_DEBUG, DEBUG_LOCK_ALLOC and
>> PROVE_LOCKING.
> PROVE_LOCKING might not be needed (and is quite heavyweight), but yes,
> enabling at the very least LOCKDEP is needed.
>
> Thanks,
>
> Mathieu
>

Indeed, the packaged kernel is built using all the default LTTng options.

Mathieu, is there a big overhead in enabling CONFIG_LOCKDEP? If not,
should it (or any other non-default options) be enabled in the package?

-- 

Alexandre Montplaisir
DORSAL lab,
École Polytechnique de Montréal