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

[Waiman Long <llong@redhat.com>]

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@redhat.com>
> 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@surriel.com>

Thanks for the review.

Cheers,
Longman