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

Lee Revell
2006-10-25T19:53:12Z

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