From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH v2] introduce atomic_pointer to fix a race condition in
 cancelable mcs spinlocks
Date: Mon, 2 Jun 2014 18:30:32 +0200
Message-ID: <20140602163032.GI16155@laptop.programming.kicks-ass.net>
References: <alpine.LRH.2.02.1406011342470.20831@file01.intranet.prod.int.rdu2.redhat.com>
 <alpine.LRH.2.02.1406021158360.20627@file01.intranet.prod.int.rdu2.redhat.com>
 <20140602162525.GH16155@laptop.programming.kicks-ass.net>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	jejb@parisc-linux.org, deller@gmx.de,
	John David Anglin <dave.anglin@bell.net>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	paulmck@linux.vnet.ibm.com, chegu_vinod@hp.com, Waiman.Long@hp.com,
	tglx@linutronix.de, riel@redhat.com, akpm@linux-foundation.org,
	davidlohr@hp.com, hpa@zytor.com, andi@firstfloor.org, aswin@hp.com,
	scott.norton@hp.com, Jason Low <jason.low2@hp.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Return-path: <linux-parisc-owner@vger.kernel.org>
In-Reply-To: <20140602162525.GH16155@laptop.programming.kicks-ass.net>
List-ID: <linux-parisc.vger.kernel.org>
List-Id: linux-parisc.vger.kernel.org

On Mon, Jun 02, 2014 at 06:25:25PM +0200, Peter Zijlstra wrote:
> I'm almost inclined to just exclude parisc from using opt spinning.
> 
> That said, this patch still doesn't address the far more interesting
> problem of actually finding these issues for these few weird archs.

So why do these archs provide xchg() and cmpxchg() at all? Wouldn't it
be much simpler if archs that cannot sanely do this, not provide these
primitives at all?