From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754582Ab0C2W7V (ORCPT ); Mon, 29 Mar 2010 18:59:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40288 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754278Ab0C2W7T (ORCPT ); Mon, 29 Mar 2010 18:59:19 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <20100329223609.GR2569@linux.vnet.ibm.com> References: <20100329223609.GR2569@linux.vnet.ibm.com> <20100329210520.GN2569@linux.vnet.ibm.com> <20100329192159.GM2569@linux.vnet.ibm.com> <20100319022527.GC2894@linux.vnet.ibm.com> <20100318133302.29754.1584.stgit@warthog.procyon.org.uk> <19192.1269889348@redhat.com> <23274.1269893706@redhat.com> <25276.1269901350@redhat.com> To: paulmck@linux.vnet.ibm.com Cc: dhowells@redhat.com, Eric Dumazet , Trond.Myklebust@netapp.com, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] NFS: Fix RCU warnings in nfs_inode_return_delegation_noreclaim() [ver #2] Date: Mon, 29 Mar 2010 23:59:03 +0100 Message-ID: <26760.1269903543@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paul E. McKenney wrote: > Only on Alpha. Otherwise only a volatile access. Whilst that is true, it's the principle of the thing. The extra barrier shouldn't be emitted on Alpha. If Alpha's no longer important, then can we scrap smp_read_barrier_depends()? My point is that some of these rcu_dereference*()'s are unnecessary. If there're required for correctness tracking purposes, fine; but can we have a macro that is just a dummy for the purpose of stripping the pointer Sparse annotation? One that doesn't invoke rcu_dereference_raw() and interpolate a barrier, pretend or otherwise, when there's no second reference to order against. David