Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752150AbbKIRdQ (ORCPT ); Mon, 9 Nov 2015 12:33:16 -0500 Received: from casper.infradead.org ([85.118.1.10]:53066 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751682AbbKIRdP (ORCPT ); Mon, 9 Nov 2015 12:33:15 -0500 Date: Mon, 9 Nov 2015 18:33:10 +0100 From: Peter Zijlstra To: Waiman Long Cc: Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Scott J Norton , Douglas Hatch , Davidlohr Bueso Subject: Re: [PATCH tip/locking/core v9 6/6] locking/pvqspinlock: Queue node adaptive spinning Message-ID: <20151109173310.GV3604@twins.programming.kicks-ass.net> References: <1446247597-61863-1-git-send-email-Waiman.Long@hpe.com> <1446247597-61863-7-git-send-email-Waiman.Long@hpe.com> <20151106150149.GV17308@twins.programming.kicks-ass.net> <563CE93E.6090000@hpe.com> <20151106203709.GD17308@twins.programming.kicks-ass.net> <5640CF08.2010001@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5640CF08.2010001@hpe.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1720 Lines: 41 On Mon, Nov 09, 2015 at 11:51:20AM -0500, Waiman Long wrote: > On 11/06/2015 03:37 PM, Peter Zijlstra wrote: > >On Fri, Nov 06, 2015 at 12:54:06PM -0500, Waiman Long wrote: > >>>>+static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev) > >>>> { > >>>> struct pv_node *pn = (struct pv_node *)node; > >>>>+ struct pv_node *pp = (struct pv_node *)prev; > >>>> int waitcnt = 0; > >>>> int loop; > >>>>+ bool wait_early; > >>>> > >>>> /* waitcnt processing will be compiled out if !QUEUED_LOCK_STAT */ > >>>> for (;; waitcnt++) { > >>>>- for (loop = SPIN_THRESHOLD; loop; loop--) { > >>>>+ for (wait_early = false, loop = SPIN_THRESHOLD; loop; loop--) { > >>>> if (READ_ONCE(node->locked)) > >>>> return; > >>>>+ if (pv_wait_early(pp, loop)) { > >>>>+ wait_early = true; > >>>>+ break; > >>>>+ } > >>>> cpu_relax(); > >>>> } > >>>> > >>>So if prev points to another node, it will never see vcpu_running. Was > >>>that fully intended? > >>I had added code in pv_wait_head_or_lock to set the state appropriately for > >>the queue head vCPU. > >Yes, but that's the head, for nodes we'll always have halted or hashed. > > The node state was initialized to be vcpu_running. In pv_wait_node(), it > will be changed to vcpu_halted before sleeping and back to vcpu_running > after that. So it is not true that it is either halted or hashed. Durh,.. I mixed up pv_wait_node() and pv_wait_head() I think. Sorry for the noise. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/