Re: [PATCH v2] x86/nmi: Add an emergency handler in nmi_desc & use it in nmi_shootdown_cpus()

[Waiman Long]

On 12/3/24 8:00 PM, Rik van Riel wrote:
> On Tue, 2024-12-03 at 10:07 -0500, Waiman Long wrote:
> > Another way to fix this problem while allowing panic() calls from
> > NMI context is by adding a new emergency NMI handler to the nmi_desc
> > structure and provide a new set_emergency_nmi_handler() helper to
> > atomically set crash_nmi_callback() in any context. The new emergency
> > handler will be invoked first before other handlers in the linked
> > list. That will eliminate the need to take any lock and serve the
> > panic
> > in NMI use case.
> >
> > Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> I've seen that panic come by a number of times, but
> never came up with a good fix.
>
> Your idea certainly looks like it should work, and
> avoid all the issues along the way.
>
> Acked-by: Rik van Riel <riel@xxxxxxxxxxx>

Thanks for the review.

Cheers,
Longman