Re: [PATCH v5 2/2] x86/mm: Improve TLB flush documentation

[Peter Zijlstra]

On Mon, Jul 24, 2017 at 09:41:39PM -0700, Andy Lutomirski wrote:
> +		/*
> +		 * Resume remote flushes and then read tlb_gen.  The
> +		 * implied barrier in atomic64_read() synchronizes

There is no barrier in atomic64_read().

> +		 * with inc_mm_tlb_gen() like this:
> +		 *
> +		 * switch_mm_irqs_off():	flush request:
> +		 *  cpumask_set_cpu(...);	 inc_mm_tlb_gen();
> +		 *  MB				 MB
> +		 *  atomic64_read(.tlb_gen);	 flush_tlb_others(mm_cpumask());
> +		 */
>  		cpumask_set_cpu(cpu, mm_cpumask(next));
>  		next_tlb_gen = atomic64_read(&next->context.tlb_gen);
>