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

[Rik van Riel]

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>

-- 
All Rights Reversed.