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 S1751231AbcFXStW (ORCPT <rfc822;w@1wt.eu>);
	Fri, 24 Jun 2016 14:49:22 -0400
Received: from bombadil.infradead.org ([198.137.202.9]:56149 "EHLO
	bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1750923AbcFXStV (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 24 Jun 2016 14:49:21 -0400
Date: Fri, 24 Jun 2016 20:48:57 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Davidlohr Bueso <dave@stgolabs.net>
Cc: mingo@kernel.org, davem@davemloft.net, cw00.choi@samsung.com,
        dougthompson@xmission.com, bp@alien8.de, mchehab@osg.samsung.com,
        gregkh@linuxfoundation.org, pfg@sgi.com, jikos@kernel.org,
        hans.verkuil@cisco.com, awalls@md.metrocast.net, dledford@redhat.com,
        sean.hefty@intel.com, kys@microsoft.com, heiko.carstens@de.ibm.com,
        James.Bottomley@HansenPartnership.com, sumit.semwal@linaro.org,
        schwidefsky@de.ibm.com, linux-kernel@vger.kernel.org,
        Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH v2 01/12] locking/atomic: Introduce inc/dec calls for
 FETCH-OP flavors
Message-ID: <20160624184857.GD30154@twins.programming.kicks-ass.net>
References: <1466453164-13185-1-git-send-email-dave@stgolabs.net>
 <1466453164-13185-2-git-send-email-dave@stgolabs.net>
 <20160621133310.GA24567@linux-80c1.suse>
 <20160621163611.GA3790@linux-80c1.suse>
 <20160623090942.GI30154@twins.programming.kicks-ass.net>
 <20160624163430.GA11823@linux-80c1.suse>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160624163430.GA11823@linux-80c1.suse>
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 Fri, Jun 24, 2016 at 09:34:30AM -0700, Davidlohr Bueso wrote:
> On Thu, 23 Jun 2016, Peter Zijlstra wrote:
> 
> >-
> >/* atomic_fetch_inc_relaxed */
> >#ifndef atomic_fetch_inc_relaxed
> >+
> >+#ifndef atomic_fetch_inc
> 
> #define atomic_fetch_inc(v)  (atomic_fetch_add(1, v))

Ah yes.

> >+#define atomic_fetch_inc_relaxed(v)	atomic_fetch_add_relaxed(1, (v))
> >+#define atomic_fetch_inc_acquire(v)	atomic_fetch_add_acquire(1, (v))
> >+#define atomic_fetch_inc_release(v)	atomic_fetch_add_release(1, (v))
> 
> I was under the impression that if the archs don't define their own calls,
> then we always default to fully ordered. Which is why I based all this ifdefery
> on what is currently done with the other atomic_fetch_$ops.

Right, but this allows an arch to only define atomic_fetch_add_relaxed()
and have the various forms of fetch_inc() instantiated as well.

With your earlier version they would all fall back to the fully
sequential variant of fetch_add().