From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755838Ab3AXVtc (ORCPT ); Thu, 24 Jan 2013 16:49:32 -0500 Received: from mail-qc0-f179.google.com ([209.85.216.179]:59734 "EHLO mail-qc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752278Ab3AXVtY (ORCPT ); Thu, 24 Jan 2013 16:49:24 -0500 Date: Thu, 24 Jan 2013 13:49:17 -0800 From: Tejun Heo To: Li Zefan Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , LKML , Cgroups Subject: Re: [PATCH v2 6/6] cgroup: remove bogus comments in cgroup_diput() Message-ID: <20130124214917.GU2373@mtj.dyndns.org> References: <5100D4FE.9080205@huawei.com> <5100D562.6050407@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5100D562.6050407@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Li. On Thu, Jan 24, 2013 at 02:32:02PM +0800, Li Zefan wrote: > Since commit 48ddbe194623ae089cc0576e60363f2d2e85662a > ("cgroup: make css->refcnt clearing on cgroup removal optional"), > each css holds a ref on cgroup's dentry, so cgroup_diput() won't be > called until all css' refs go down to 0, which invalids the comments. > > Signed-off-by: Li Zefan > --- > kernel/cgroup.c | 6 ------ > 1 file changed, 6 deletions(-) > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index f18b0d9..368cff1 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -899,12 +899,6 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode) > struct cgroup *cgrp = dentry->d_fsdata; > > BUG_ON(!(cgroup_is_removed(cgrp))); > - /* It's possible for external users to be holding css > - * reference counts on a cgroup; css_put() needs to > - * be able to access the cgroup after decrementing > - * the reference count in order to know if it needs to > - * queue the cgroup to be handled by the release > - * agent */ The latter half is still true tho. I applied the patch anyway as the comment isn't all that useful without covering everything intended to be covered with RCU. Can you please write up another patch documenting what's covered by RCU (stuff that we intend to keep guaranteeing to be safe to access only w/ RCU)? Thanks. -- tejun