Re: [PATCH v2 11/11] mm,sched: conditionally skip lazy TLB mm refcounting

From: Peter Zijlstra
Date: Tue Jul 31 2018 - 05:13:18 EST


On Mon, Jul 30, 2018 at 09:05:55PM -0400, Rik van Riel wrote:
> On Mon, 2018-07-30 at 18:26 +0200, Peter Zijlstra wrote:
> >
> > So for ARCH_NO_ACTIVE_MM we never touch ->active_mm and therefore
> > ->active_mm == ->mm.
>
> Close, but not true for kernel threads, which have a
> NULL ->mm, but a non-null ->active_mm that gets passed
> to enter_lazy_tlb().

I'm confused on the need for this. We mark the CPU lazy, why do we still
care about this?

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