Re: [ltt-dev] lttctl locks up with RT Linux

[Mathieu Desnoyers <compudj@krystal.dyndns.org>]

Please double-check that you applied the last patch correctly. I tried
building a lttng-enabled -rt tree here (x86 64 box), and it works (I can
start/stop tracing and see the trace in lttv).

Note that I simply discarded the conflicting instrumentation patches for
this quick test.

I'm pretty sure an error could have been inserted in async_wakeup()
within ltt-tracer.c. Can you paste the code you have ?

Unbalanced rcu read lock/unlock could be causing this.

Thanks,

Mathieu

* jpaul@gdrs.com (jpaul@gdrs.com) wrote:
> Turning off CONFIG_RCU_CPU_STALL_DETECTOR does not solve the issue with starting up "lttctl -C" ... that call never returns. I'm no longer getting the stack dumps in /var/log/messages and I still have to hard reboot the system as soft reboot doesn't work.
> 
> JP
> 
> 
> -----Original Message-----
> From: Mathieu Desnoyers [mailto:compudj@krystal.dyndns.org]
> Sent: Tue 5/11/2010 11:11 AM
> To: John P. Paul
> Cc: ltt-dev@lists.casi.polymtl.ca; Paul E. McKenney; linux-rt-users@vger.kernel.org
> Subject: Re: [ltt-dev] lttctl locks up with RT Linux
>  
> * jpaul@gdrs.com (jpaul@gdrs.com) wrote:
> > Thanks Mathieu. I'm going to have to look at this a bit more. This may
> > have fixed one problem and cause another as "lttctl -C -w /tmp/trace
> > trace1" does not return and I'm getting a stack dump in the messages
> > file (see below). The last msg I see from that "lttctl -C" command is
> > "lttctl: Creating trace". The "lttctl: Forking lttd" is not displayed.
> 
> If you disable RCU stalls detection, does it work ?
> 
> [Context for Paul: it's on a -RT kernel, with the LTTng patchset]
> 
> Thanks,
> 
> Mathieu
> 
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-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com