linux-kernel - Re: [PATCH] x86/mm: Add barriers and document switch

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Message-ID: <20160802231229.GE32028@t510>
Date:	Tue, 2 Aug 2016 19:12:30 -0400
From:	Rafael Aquini <aquini@...hat.com>
To:	Nadav Amit <nadav.amit@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>,
	X86 ML <x86@...nel.org>, Andy Lutomirski <luto@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>, lwoodman@...hat.com,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] x86/mm: Add barriers and document switch_mm()-vs-flush
 synchronization follow-up

On Tue, Aug 02, 2016 at 03:27:06PM -0700, Nadav Amit wrote:
> Rafael Aquini <aquini@...hat.com> wrote:
> 
> > While backporting 71b3c126e611 ("x86/mm: Add barriers and document switch_mm()-vs-flush synchronization")
> > we stumbled across a possibly missing barrier at flush_tlb_page().
> 
> I too noticed it and submitted a similar patch that never got a response [1].
>

As far as I understood Andy's rationale for the original patch you need
a full memory barrier there in flush_tlb_page to get that cache-eviction
race sorted out.

Regards,
-- Rafael