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

On Wed, Mar 22, 2017 at 1:14 PM, Dmitry Vyukov <dvyukov@google.com> wrote:
> On Wed, Mar 22, 2017 at 12:30 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>> On Wed, Mar 22, 2017 at 11:42 AM, Dmitry Vyukov <dvyukov@google.com> wrote:
>>> On Tue, Mar 21, 2017 at 10:20 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>>> On Tue, Mar 21, 2017 at 7:06 PM, Dmitry Vyukov <dvyukov@google.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

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