linux-kernel - Re: [PATCH 2/3] asm-generic, x86: wrap atomic operations

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Message-ID: <CAK8P3a1nheF5bWw67M0vpdo3F_O-ChQTgH6cgw_ATtYuLZumHw@mail.gmail.com>
Date:   Wed, 22 Mar 2017 13:48:37 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] asm-generic, x86: wrap atomic operations

On Wed, Mar 22, 2017 at 1:14 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> On Wed, Mar 22, 2017 at 12:30 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> On Wed, Mar 22, 2017 at 11:42 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>>> On Tue, Mar 21, 2017 at 10:20 PM, Arnd Bergmann <arnd@...db.de> wrote:
>>>> On Tue, Mar 21, 2017 at 7:06 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>>>
>>> Initially I've tested with my stock gcc 4.8.4 (Ubuntu
>>> 4.8.4-2ubuntu1~14.04.3) and amusingly it works. But I can reproduce
>>> the bug with 7.0.1.
>>
>> It's probably because gcc-4.8 didn't support KASAN yet, so the added
>> check had no effect.
>
> I've tested without KASAN with both compilers.

Ah ok. I had not realized that this happened even without KASAN. I only saw this
problem in one out of hundreds of defconfig builds and assumed it was related
since this came from a kasan change.

      Arnd