From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH v2 6/6] cgroup: remove bogus comments in cgroup_diput() Date: Fri, 25 Jan 2013 10:27:24 +0800 Message-ID: <5101ED8C.9030205@huawei.com> References: <5100D4FE.9080205@huawei.com> <5100D562.6050407@huawei.com> <20130124214917.GU2373@mtj.dyndns.org> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130124214917.GU2373-9pTldWuhBndy/B6EtB590w@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Andrew Morton , Peter Zijlstra , Ingo Molnar , LKML , Cgroups > 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)? > Sure. I'll try.