On Tue, Aug 01, 2017 at 03:58:49PM +0200, Peter Zijlstra wrote:

On Tue, Aug 01, 2017 at 06:43:14AM -0700, Andy Lutomirski wrote:

quoted

Anyway, can you document whatever property you require with a comment
in switch_mm() or wherever you're finding that property so that future
arch changes don't break it?

We need _a_ smp_mb after rq->curr store. x86 has plenty.

That is, we need it when we change to a different !0 mm. And we have the
mm_cpumask() atomics at the very least, even if loading a new CR3 would
not be serializing.