From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: Re: [PATCH v2] introduce atomic_pointer to fix a race condition in cancelable mcs spinlocks Date: Mon, 2 Jun 2014 09:46:55 -0700 Message-ID: <20140602164655.GT22231@linux.vnet.ibm.com> References: <20140602162525.GH16155@laptop.programming.kicks-ass.net> <20140602163032.GI16155@laptop.programming.kicks-ass.net> Reply-To: paulmck@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii 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, 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 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 Mon, Jun 02, 2014 at 06:30:32PM +0200, 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? Such architectures would also need to avoid NO_HZ_FULL_SYSIDLE and RCU_NOCB_CPU, but those are probably entirely reasonable restrictions. Thanx, Paul