Re: [PATCH] kthread: Prevent unpark race which puts threads on thewrong cpu

[Thomas Gleixner]

Dave,

On Tue, 9 Apr 2013, Dave Hansen wrote:

> Hey Thomas,
> 
> I don't think the patch helped my case.  Looks like the same BUG_ON().
> 
> I accidentally booted with possible_cpus=10 instead of 160.  I wasn't
> able to trigger this in that case, even repeatedly on/offlining them.
> But, once I booted with possible_cpus=160, it triggered in a jiffy.

Darn. We should have merged Paul McKenneys NR_CPUS=0 patch last year
and we would have avoided the whole shebang.
 
> > [  161.551788] smpboot_thread_fn():
> > [  161.551807] td->cpu: 132
> > [  161.551808] smp_processor_id(): 121
> > [  161.551811] comm: migration/%u
> > [  161.551840] ------------[ cut here ]------------
> > [  161.551939] kernel BUG at kernel/smpboot.c:149!

Any chance, that you get a trace for that?

Thanks,

	tglx

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/