linux-kernel - Re: [PATCH v5 00/18] Rework READ

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Message-ID: <20200515140720.GE2940@hirez.programming.kicks-ass.net>
Date:   Fri, 15 May 2020 16:07:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     Marco Elver <elver@...gle.com>, Will Deacon <will@...nel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v5 00/18] Rework READ_ONCE() to improve codegen

On Fri, May 15, 2020 at 01:55:43PM +0000, David Laight wrote:
> From: Peter Zijlstra
> > Sent: 14 May 2020 15:25
> ..
> > Exact same requirements, KASAN even has the data_race() problem through
> > READ_ONCE_NOCHECK(), UBSAN doesn't and might be simpler because of it.
> 
> What happens if you implement READ_ONCE_NOCHECK() with an
> asm() statement containing a memory load?
> 
> Is that enough to kill all the instrumentation?

You'll have to implement it for all archs, but yes, I think that ought
to work.