Re: oprofile can cause an NMI to schedule (was: [RT] schedulingand oprofile)

[Lee Revell]

On Wed, 2006-10-25 at 11:58 -0700, Mike Kravetz wrote:
> Newer RT kernels (such as linux-2.6.18-rt5) have reenabled the
> add_preempt_count/sub_preempt_count calls in nmi_enter/exit.  If I
> understand correctly the reason one could not modify the preempt_count
> from NMI code is that it could have been in the process of being
> modified by non-NMI code.  But, in recent RT kernels it appears that
> preempt_count is still a single word modified by both NMI and
> non-NMI code.  What am I missing that now makes this safe?
> 

It's not safe.  NMI causes hard lockups on 2.6.18-rt5.  Get 2.6.18-rt7.

Lee

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