From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S935050AbdCXSFN (ORCPT <rfc822;w@1wt.eu>);
        Fri, 24 Mar 2017 14:05:13 -0400
Received: from merlin.infradead.org ([205.233.59.134]:32940 "EHLO
        merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S934492AbdCXSEy (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 24 Mar 2017 14:04:54 -0400
Date: Fri, 24 Mar 2017 19:04:41 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Dmitry Vyukov <dvyukov@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>, Denys Vlasenko <dvlasenk@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Josh Poimboeuf <jpoimboe@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: locking/atomic: Introduce atomic_try_cmpxchg()
Message-ID: <20170324180441.gj5uhlttdzt7zxod@hirez.programming.kicks-ass.net>
References: <CACT4Y+bG+a0w6j6v1AmBE7fqqMSPyPEm4QimCzCouicmHT8FqA@mail.gmail.com>
 <20170324142140.vpyzl755oj6rb5qv@hirez.programming.kicks-ass.net>
 <20170324164108.ibcxxqbhvx6ao54r@hirez.programming.kicks-ass.net>
 <CALCETrVFOKC91hKWxm+-w2v2FPGJ37RoCOYX5FYpszjMrAaUOQ@mail.gmail.com>
 <20170324172342.radlrhk2z6mwmdgk@hirez.programming.kicks-ass.net>
 <20170324180025.tumlczzf4ji3uzpo@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20170324180025.tumlczzf4ji3uzpo@hirez.programming.kicks-ass.net>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Mar 24, 2017 at 07:00:25PM +0100, Peter Zijlstra wrote:
> static inline bool try_cmpxchg2(unsigned int *ptr, unsigned int *val, unsigned int new)
> {
> 	unsigned int old = *val;
> 	bool success;
> 
>         asm volatile goto("lock cmpxchgl %[new], %[ptr]; "
>                           "jnz %[label]"
>                      : /* no output */
>                      : [ptr] "+m" (*ptr),
>                        [old] "+a" (old)
>                        [new] "r" (new)
>                      : "memory"
>                      : label);
>         return 1;
> 
> label:
> 	*val = old;
> 	return 0;
> }

N/m, I'm apparently so tired I didn't see the compiler errors :/