From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks Date: Mon, 02 Jun 2014 13:33:34 -0400 Message-ID: <538CB56E.5010709@hp.com> References: <20140602162525.GH16155@laptop.programming.kicks-ass.net> <20140602163032.GI16155@laptop.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: Mikulas Patocka , Linus Torvalds , jejb@parisc-linux.org, deller@gmx.de, John David Anglin , linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, paulmck@linux.vnet.ibm.com, chegu_vinod@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 To: Peter Zijlstra Return-path: In-Reply-To: <20140602163032.GI16155@laptop.programming.kicks-ass.net> List-ID: List-Id: linux-parisc.vger.kernel.org On 06/02/2014 12:30 PM, Peter Zijlstra wrote: > 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? I believe xchg() and cmpxchg() are used in quite a number of places within the generic kernel code. So kernel compilation will fail if those APIs aren't provided by an architecture. -Longman