Re: [Xenomai-help] Sporadic PC freeze after rt_task_start

[Jan Kiszka <jan.kiszka@domain.hid>]

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M. Koehrer wrote:
> Hi!
> 
> After a couple of over-night test runs, I finally got an NMI watchdog detected lockup with the sporadic freeze option.
> I started the system with the argument nmi_watchdog=1 (also isolcpus=1).
> See the code below. As I have not connected a serial console, I have attached a screen shot in a fairly
> bad quality as jpg file... However, it is good enough to be able to read everything... 
> The lockup is in function rpi_pop [xeno_nucleus].
> It is called from gatekeeper_thread and from default_wake_function.
> See the attached jpg for details.

Looks like we are stuck on rpilock, Philippe.

And when looking at the holders of rpilock, I think one issue could be
that we hold that lock while calling into xnpod_renice_root [1], ie.
doing a potential context switch. Was this checked to be save?
Furthermore, that code path reveals that we take nklock nested into
rpilock [2]. I haven't found a spot for the other way around (and I hope
there is none), but such nesting is already evil per se...

Mathias, already tried your test case with our old friend "priority
coupling" switched off? *If* this lock-up is actually due to rpilock
brokenness, switching the feature off should make it disappear.

Jan


[1]http://www.rts.uni-hannover.de/xenomai/lxr/source/ksrc/nucleus/shadow.c?v=SVN-trunk#435
[2]http://www.rts.uni-hannover.de/xenomai/lxr/source/include/nucleus/pod.h?v=SVN-trunk#308


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