Crashes and anomaly with debug/tracing

[Kamal Mostafa]

On Wed, May 04, 2016 at 03:37:51PM +0200, Xen wrote:
> I am on a 16.04 Kubuntu system installed on USB 2.0 with kernel
> 4.4.0-21-generic #37-Ubuntu SMP on x86_64.

Hi-

Several tracer-related fixes landed in the next Xenial 16.04 kernel
verion (4.4.0-22.38) which is currently pending in "-proposed":
https://launchpad.net/ubuntu/+source/linux/4.4.0-22.38

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how
to enable and use -proposed.

Please test that -proposed kernel, and if you still experience problems,
then please do file a bug in Launchpad against the 'linux' package.

Thanks,

 -Kamal


> Previously I was running the same system in a live session.
> 
> When I echo "function" to /sys/kernel/debug/tracing/current_tracer, the
> system reboots.
> 
> Only the first trace I can get after reboot is helpful. I do not seem to be
> able to get the output I want after.
> 
> I might have a lot of output but my function call is not actually in there.
> 
> My method is to turn the tracer on (1 > tracing_on) and then run my program,
> and then turn it off again.
> 
> If I echo 1 > free_buffer the output is botched and I get only very meager
> output (say 40 lines) and not what I want. "function_graph" does work and
> does not reboot the system.
> 
> While inserting a module that did nothing special and worked as intended
> (very small test module so to speak), if the tracer was on (function_graph)
> and I did insmod, the kernel would panic and I think also freeze.
> 
> So I could not trace anything happening in my module or its calls.
> 
> Before I installed the system and I was running from DVD with a cache
> partition on harddisk, the tracer seemed to have worked better and
> free_buffers seemed not to have caused that aberrant behaviour.
> 
> Currently though I cannot free the buffer or the output gets botched
> (severely limited output) and without clearing it apparently I also do not
> get the output I want, so it comes down to running one trace per reboot and
> that's it.
> 
> I don't know if this needs to be said anywhere else but they told me to go
> here first.
> 
> I have not filed a bug.
> 
> Regards.
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team