linux-kernel - Re: [OpenRISC] [PATCH v3 08/25] openrisc: add cmpxchg and xchg implementations

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Message-ID: <a846d63e-14cd-7b29-54d8-b361cd74c522@twiddle.net>
Date:   Thu, 23 Feb 2017 04:30:35 +1100
From:   Richard Henderson <rth@...ddle.net>
To:     Stafford Horne <shorne@...il.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Jonas Bonn <jonas@...thpole.se>, openrisc@...ts.librecores.org,
        linux-kernel@...r.kernel.org, linux@...ck-us.net
Subject: Re: [OpenRISC] [PATCH v3 08/25] openrisc: add cmpxchg and xchg
 implementations

On 02/23/2017 01:20 AM, Stafford Horne wrote:
> On Wed, Feb 22, 2017 at 12:19:40PM +0100, Peter Zijlstra wrote:
>> On Wed, Feb 22, 2017 at 04:11:37AM +0900, Stafford Horne wrote:
>>> +	__asm__ __volatile__(
>>> +		"1:	l.lwa %0, 0(%1)		\n"
>>> +		"	l.sfeq %0, %2		\n"
>>> +		"	l.bnf 1f		\n"
>>> +		"	 l.nop			\n"
>>> +		"	l.swa 0(%1), %3		\n"
>>> +		"	l.bnf 1b		\n"
>>> +		"1:	 l.nop			\n"
>>> +		: "=&r"(old)
>>> +		: "r"(ptr), "r"(old), "r"(new)
>>> +		: "cc", "memory");
>>
>> I just noticed this, but having both labels have the same name is
>> somewhat confusing.
>
> Right, better to use '2' for the second one.

Better still to put the second label after the delay-slot nop.
You don't need to execute that on the way out.


r~