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

quoted

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