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Subject: Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
To: Borislav Petkov <bp@alien8.de>
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Cc: Peter Zijlstra <peterz@infradead.org>, Michal Hocko <mhocko@kernel.org>,
        Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
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        Tony Luck <tony.luck@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Chris Zankel <chris@zankel.net>, Max Filippov <jcmvbkbc@gmail.com>,
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        linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
        linux-xtensa@linux-xtensa.org, linux-arch@vger.kernel.org,
        Josh Poimboeuf <jpoimboe@redhat.com>
From: "H. Peter Anvin" <hpa@zytor.com>
Message-ID: <5717EF59.1030709@zytor.com>
Date: Wed, 20 Apr 2016 14:06:33 -0700
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On 04/20/2016 01:45 PM, Borislav Petkov wrote:
> On Wed, Apr 20, 2016 at 11:04:05AM -0700, H. Peter Anvin wrote:
>> The reason it breaks is because the same register can't be an
>> input-output register and a separate input. However, the input side of
>> the input-output is probably undefined, and so gcc may not notice.
> 
> So Michal and I talked about this a while ago. Why do we need the '"a"
> (sem)' input dependency if '"+a" (ret)' already supplies the same thing?
> 

Setting ret to sem doesn't make any sense.  Just use "=a" and "a".

	-hpa