Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752095AbXB0UcE (ORCPT ); Tue, 27 Feb 2007 15:32:04 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752129AbXB0UcE (ORCPT ); Tue, 27 Feb 2007 15:32:04 -0500 Received: from smtp.osdl.org ([65.172.181.24]:50579 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752095AbXB0UcB (ORCPT ); Tue, 27 Feb 2007 15:32:01 -0500 Date: Tue, 27 Feb 2007 12:25:17 -0800 From: Andrew Morton To: Oleg Nesterov Cc: hugh@veritas.com, paulmck@linux.vnet.ibm.com, clameter@sgi.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] adapt page_lock_anon_vma() to PREEMPT_RCU Message-Id: <20070227122517.c8bceaf5.akpm@linux-foundation.org> In-Reply-To: <20070225200621.GA2259@tv-sign.ru> References: <20070225200621.GA2259@tv-sign.ru> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.19; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 910 Lines: 24 > On Sun, 25 Feb 2007 23:06:21 +0300 Oleg Nesterov wrote: > page_lock_anon_vma() uses spin_lock() to block RCU. This doesn't work with > PREEMPT_RCU, we have to do rcu_read_lock() explicitely. Otherwise, it is > theoretically possible that slab returns anon_vma's memory to the system > before we do spin_unlock(&anon_vma->lock). > > ... > > +static void page_unlock_anon_vma(struct anon_vma *anon_vma) > +{ > + spin_unlock(&anon_vma->lock); > + rcu_read_unlock(); > } It's a bit sad doing a double preempt_disable() for non-PREEMPT_RCU builds. Perhaps we would benefit from a new rcu_read_lock_preempt_rcu() which is a no-op if !PREEMPT_RCU. - 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/