Re: [PATCH v2 6/6] cgroup: remove bogus comments in cgroup_diput()

Li Zefan
2013-01-25T02:29:20Z

> 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 <lizefan@huawei.com>
>> ---
>> 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.