machdep.hlt_cpus not safe with ULE?

Gary Jennejohn gljennjohn at
Sat Feb 19 14:05:29 UTC 2011

On Sat, 19 Feb 2011 12:36:57 -0000
"Steven Hartland" <killing at> wrote:

> I'm trying to debug a possibly failing CPU, so I thought it would
> be easy just disable the cores using machdep.hlt_cpus and see if
> we see the panic's we've been seeing.
> The problem is it seems ULE doesnt properly support machdep.hlt_cpus
> and still schedules processes onto the halted cpus which obviously
> causes problems.
> Can anyone confirm this behaviour? Should machdep.hlt_cpus and I assume
> the logical counterpart never be used with ULE?

Looking at the kernel source it appears that only sched_4bsd.c makes use
of hlt_cpus_mask.

Gary Jennejohn

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