[lttng-dev] lttclt hungs on destroying traces on (PREEMPT_RT)

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Mon Feb 20 09:42:47 EST 2012

* Piotr Romaniuk (piotr.romaniuk at elesoftrom.com.pl) wrote:
> Hi,
> I have a problem with getting traces on kernel with PREEMPT_RT  
> patch.
> I can run ltt-armall and create traces by lttctl but when I destroy  
> traces  lttclt hungs.
> Is there any fundamental obstacle in RT-kernel for LTT?
> I use following versions:
> 1) kernel
> 2) patch- from  
> http://www.kernel.org/pub/linux/kernel/projects/rt/2.6.33/older/
> 3) LTTng: patch-
> 4) LTT control: 0.89-05122011
> I tuned slightly LTTng patches in order to apply them on rt kernel.
> The changes were rather easy and were limited to adaptation of  
> surrounding context
> that had been changed by RT-patch.
> I built the kernel (all LTT modules I built in the kernel) successfully.
> The problem appears when I try to destroy traces. Lttctl hungs and no  
> data are copied to files.
> Do you have any suggestions?

You should grep for "CONFIG_PREEMPT_RT" within later versions of lttng
0.x. Modifications were done to locking to support RT, and without those
the destroy operation was hanging.

If this does not work out for you, you should probably move to LTTng 2.0
prereleases, since LTTng 0.x is not supported anymore.



> Regards,
> Piotr Romaniuk
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.

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