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 S1752237AbcFFL5K (ORCPT <rfc822;w@1wt.eu>);
	Mon, 6 Jun 2016 07:57:10 -0400
Received: from merlin.infradead.org ([205.233.59.134]:54461 "EHLO
	merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751073AbcFFL5I (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 6 Jun 2016 07:57:08 -0400
Date: Mon, 6 Jun 2016 13:56:55 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Will Deacon <will.deacon@arm.com>, Boqun Feng <boqun.feng@gmail.com>
Subject: Re: [PATCH v3] powerpc: spinlock: Fix spin_unlock_wait()
Message-ID: <20160606115655.GD30909@twins.programming.kicks-ass.net>
References: <1465213340.2658.1.camel@ellerman.id.au>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1465213340.2658.1.camel@ellerman.id.au>
User-Agent: Mutt/1.5.23.1 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, Jun 06, 2016 at 09:42:20PM +1000, Michael Ellerman wrote:
> +static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
> +{
> +	arch_spinlock_t lock_val;
> +
> +	smp_mb();
> +
> +	/*
> +	 * Atomically load and store back the lock value (unchanged). This
> +	 * ensures that our observation of the lock value is ordered with
> +	 * respect to other lock operations.
> +	 */
> +	__asm__ __volatile__(
> +"1:	" PPC_LWARX(%0, 0, %2, 0) "\n"
> +"	stwcx. %0, 0, %2\n"
> +"	bne- 1b\n"
> +	: "=&r" (lock_val), "+m" (*lock)
> +	: "r" (lock)
> +	: "cr0", "xer");
> +
> +	if (arch_spin_value_unlocked(lock_val))
> +		goto out;
> +
> +	while (!arch_spin_value_unlocked(*lock)) {
> +		HMT_low();
> +		if (SHARED_PROCESSOR)
> +			__spin_yield(lock);
> +	}
> +	HMT_medium();
> +
> +out:
> +	smp_mb();
> +}

Why the move to in-line this implementation? It looks like a fairly big
function.