Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966361AbaFRLnQ (ORCPT ); Wed, 18 Jun 2014 07:43:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:62864 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965572AbaFRLnO (ORCPT ); Wed, 18 Jun 2014 07:43:14 -0400 Message-ID: <53A17B15.3080904@redhat.com> Date: Wed, 18 Jun 2014 13:42:13 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Peter Zijlstra , Waiman.Long@hp.com, tglx@linutronix.de, mingo@kernel.org CC: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, paolo.bonzini@gmail.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com, paulmck@linux.vnet.ibm.com, riel@redhat.com, torvalds@linux-foundation.org, raghavendra.kt@linux.vnet.ibm.com, david.vrabel@citrix.com, oleg@redhat.com, gleb@redhat.com, scott.norton@hp.com, chegu_vinod@hp.com, Peter Zijlstra Subject: Re: [PATCH 06/11] qspinlock: Optimize pending bit References: <20140615124657.264658593@chello.nl> <20140615130153.638054585@chello.nl> In-Reply-To: <20140615130153.638054585@chello.nl> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 15/06/2014 14:47, Peter Zijlstra ha scritto: > XXX: merge into the pending bit patch.. Agree, or if not move it right after the pending bit patch, before the NR_CPUS optimization. Paolo > It is possible so observe the pending bit without the locked bit when > the last owner has just released but the pending owner has not yet > taken ownership. > > In this case we would normally queue -- because the pending bit is > already taken. However, in this case the pending bit is guaranteed to > be released 'soon', therefore wait for it and avoid queueing. > > Signed-off-by: Peter Zijlstra -- 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/