[ltt-dev] lttctl locks up with RT Linux

[jpaul at gdrs.com]

Thanks Mathieu.  This was my fault .. I couldn't apply your patch (kept getting failures on hunks 2-8 for some reason) so I hand patched the file and in doing so, transposed a rcu unlock with an rcu lock (just as you suspected). So, after correcting that, all is well and I'm able to perform tracing under 2.6.33.2 RT.

Thanks Much!

JP


-----Original Message-----
From: Mathieu Desnoyers [mailto:compudj at krystal.dyndns.org]
Sent: Thu 5/13/2010 2:23 PM
To: John P. Paul
Cc: ltt-dev at lists.casi.polymtl.ca; paulmck at linux.vnet.ibm.com; linux-rt-users at vger.kernel.org
Subject: Re: [ltt-dev] lttctl locks up with RT Linux
 
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 at gdrs.com (jpaul at 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

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