Subject: Re: [PATCH v2 1/5] printk/nmi: Generic solution for safe printk in NMI

From: Petr Mladek <[email-masked]>
Date: Mon, 30 Nov 2015 15:25:45 +0100

On Fri 2015-11-27 17:26:16, Max Filippov wrote:
Hi Max,

> > Another exception is Xtensa architecture that uses just a
> > fake NMI.
> 
> It's called fake because it's actually maskable, but sometimes
> it is safe to use it as NMI (when there are no other IRQs at the
> same priority level and that level equals EXCM level). That
> condition is checked in arch/xtensa/include/asm/processor.h
> So 'fake' here is to avoid confusion with real NMI that exists
> on xtensa (and is not currently used in linux), otherwise code
> that runs in fake NMI must follow the NMI rules.
> 
> To make xtensa compatible with your change we can add a
> choice whether fake NMI should be used to kconfig. It can
> then set HAVE_NMI accordingly. I'll post a patch for xtensa.

Thanks a lot for explanation. I'll wait for the destiny of
the patch adding CONFIG_XTENSA_FAKE_NMI. It is not easy
for me to review. Anyway, we could select HAVE_NMI for
Xtensa anytime later if this patchset goes in earlier.

Best Regards,
Petr