Re: [Xenomai] two dd processes: soft lockup

[Jan Kiszka <jan.kiszka@web.de>]

On 2013-08-22 09:59, Benedikt Boeck wrote:
> Hello,
> 
> I got a problem. After starting two dd processes (if=/dev/zero
> of=/dev/null), I get first a few messages about soft lockup:
> kernel:[...] BUG: soft lockup - CPU#. stuck for ..s! [dd:...]
> and little later a
> Kernel panic - not syncing: Fatal exception in interrupt
> 
> But if I had running xeno-test before and then starting two dd processes
> I don't get a soft lockup. Strange?
> 
> Also there is no soft lockup with a kernel identical till a deactivated
> CONFIG_XENOMAI.
> A deactivated CONFIG_SMP also prevent the error. But I like to have both
> cores. Trying all four variants of CONFIG_SCHED_SMT=y/n and
> CONFIG_SCHED_MC=y/n didn't effect the error.
> 
> Tested with different kernel versions (3.4.6, 3.5.7, 3.8) always with
> matching ipipe patch.  I think with 3.8 I didn't get a kernel panic but
> still soft lockups.
> Using Xenomai 2.6.2.1 and haven't tried other versions yet. The
> processor is a Celeron Dual-Core T3100.
> 
> Does somebody have a idea? Maybe I just made a simple (but effective)
> mistake.

I've tried your configuration on ipipe-3.8 [1] but wasn't able to
reproduced it in a 2-cpu VM with 2 dd instances. Could you provide the
3.8 config as well that generates the warnings for you? And please
provide the information Gilles asked for,

Thanks,
Jan

[1] http://git.xenomai.org/?p=ipipe.git;a=shortlog;h=refs/heads/ipipe-3.8


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