Re: [PATCH 7/7] x86/mm: Switch to generic get_user_page_fast() implementation

[Peter Zijlstra]

On Thu, Mar 16, 2017 at 06:26:55PM +0300, Kirill A. Shutemov wrote:
> +config HAVE_GENERIC_RCU_GUP
> +	def_bool y
> +

Nothing immediately jumped out to me; except that this option might be
misnamed.

AFAICT that code does not in fact rely on HAVE_RCU_TABLE_FREE; it will
happily work with the (x86) broadcast IPI invalidate model, as you show
here.

Architectures that do not do that obviously need HAVE_RCU_TABLE_FREE,
but that is not the point I feel.

Also, this code hard relies on IRQ-disable delaying grace periods, which
is mostly true I think, but has always been something Paul didn't really
want to commit too firmly to.