Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933586AbXBXXBe (ORCPT ); Sat, 24 Feb 2007 18:01:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933588AbXBXXBd (ORCPT ); Sat, 24 Feb 2007 18:01:33 -0500 Received: from pool-71-111-73-6.ptldor.dsl-w.verizon.net ([71.111.73.6]:6494 "EHLO IBM-8EC8B5596CA.beaverton.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S933586AbXBXXBc (ORCPT ); Sat, 24 Feb 2007 18:01:32 -0500 Date: Sat, 24 Feb 2007 14:36:55 -0800 From: "Paul E. McKenney" To: Hugh Dickins Cc: Oleg Nesterov , dipankar@in.ibm.com, Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: PREEMPT_RCU breaks anon_vma locking ? Message-ID: <20070224223655.GG5049@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20070223212303.GA423@tv-sign.ru> <20070223224145.GD1630@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1131 Lines: 24 On Sat, Feb 24, 2007 at 10:10:57PM +0000, Hugh Dickins wrote: > On Fri, 23 Feb 2007, Paul E. McKenney wrote: > > > > This look like a valid fix to me, at least as long as the lock is never > > dropped in the meantime (e.g., to do I/O). If the lock -is- dropped in > > the meantime, then presumably whatever is done to keep the page from > > vanishing should allow an rcu_read_unlock() to be placed after each > > spin_unlock(&...->lock) and an rcu_read_lock() to be placed before each > > spin_lock(&...->lock). > > Thankfully no complications of that kind, page_lock_anon_vma is static > to mm/rmap.c, and only used to hold the spin lock while examining page > tables of the vmas in the list, never a need to drop that lock at all. > (Until the day when someone reports such a long list that we start to > worry about the latency.) Whew!!! For now, anyway! ;-) Thanx, Paul - 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/