Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752560AbZGLWMx (ORCPT ); Sun, 12 Jul 2009 18:12:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751426AbZGLWMp (ORCPT ); Sun, 12 Jul 2009 18:12:45 -0400 Received: from tundra.namei.org ([65.99.196.166]:32966 "EHLO tundra.namei.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751676AbZGLWMp (ORCPT ); Sun, 12 Jul 2009 18:12:45 -0400 Date: Mon, 13 Jul 2009 08:12:13 +1000 (EST) From: James Morris To: David Howells cc: Oleg Nesterov , Christoph Hellwig , Andrew Morton , "Paul E. McKenney" , Roland McGrath , Stephen Smalley , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 -mm 2/2] current_is_single_threaded: don't use ->mmap_sem In-Reply-To: <25973.1247234862@redhat.com> Message-ID: References: <20090710014857.GC4723@redhat.com> <20090709212847.GA10238@redhat.com> <20090710013322.GA27719@infradead.org> <25973.1247234862@redhat.com> User-Agent: Alpine 2.00 (LRH 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 897 Lines: 27 On Fri, 10 Jul 2009, David Howells wrote: > > However we can avoid ->mmap_sem and rely on rcu/barriers: > > > > - if we do not see the exiting parent on thread/process list > > we see the result of list_del_rcu(), in this case we must > > also see the result of list_add_rcu() which does wmb(). > > > > - if we do see the parent but its ->mm == NULL, we need rmb() > > to make sure we can't miss the child. > > > > Signed-off-by: Oleg Nesterov > > Acked-by: David Howells I gather this stuff is going into -mm ? Can it be merged via security-testing#next? -- James Morris -- 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/