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From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Mon, 13 Jul 2015 20:25:04 +0200
Message-ID: <CAK1hOcNvBvHQ22YiS0LQ6mr1z2YLmmsCKAEB6Hr+ac9PkQf3ww@mail.gmail.com>
Subject: Re: [PATCH RFC] x86: enforce inlining for atomics
To: Markus Trippelsdorf <markus@trippelsdorf.de>
Cc: Hagen Paul Pfeifer <hagen@jauu.net>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Borislav Petkov <bp@alien8.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>
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On Wed, Apr 22, 2015 at 11:20 AM, Markus Trippelsdorf
<markus@trippelsdorf.de> wrote:
> On 2015.04.22 at 07:58 +0200, Hagen Paul Pfeifer wrote:
>> * Markus Trippelsdorf | 2015-04-22 07:24:41 [+0200]:
>> >I cannot reproduce this issue with my config with 4.8, 4.9 or 5. Could
>> >you please come up with a small testcase and open a gcc bug (with full
>> >gcc command line)?
>>
>> the attached config file should do the trick. Can you try it?
>
> It is definitely a -O2 vs. -Os issue. With your config:


It's true that it happens more often with -Os, but -O2 is not immune either.

See comments in the gcc bug:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
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