[PATCH 1/4] mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[peterz at infradead.org]

On Fri, Aug 28, 2020 at 08:00:19PM +1000, Nicholas Piggin wrote:

> Closing this race only requires interrupts to be disabled while ->mm
> and ->active_mm are being switched, but the TLB problem requires also
> holding interrupts off over activate_mm. Unfortunately not all archs
> can do that yet, e.g., arm defers the switch if irqs are disabled and
> expects finish_arch_post_lock_switch() to be called to complete the
> flush; um takes a blocking lock in activate_mm().

ARM at least has activate_mm() := switch_mm(), so it could be made to
work.