Hello, Li.
On Tue, Sep 02, 2014 at 06:56:58PM +0800, Li Zefan wrote:
> for ((; ;))
> {
> echo $$ > /cgroup/sub/cgroup.procs
> ech $$ > /cgce 6f2e0c38c2108a74 ]---
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
copy & paste error?
...
> Reported-by: Toralf Förster <toralf.foerster@xxxxxx>
> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
> ---
>
> Toralf, Thanks for reporting the bug. I'm not able to repy to your email,
> because I was kicked out of the cgroup mailing list so didn't receive
> emails from mailing list for a week.
>
> ---
> kernel/cgroup.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 1c56924..e03fc62 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -4185,6 +4185,15 @@ static void css_release_work_fn(struct work_struct *work)
>
> mutex_unlock(&cgroup_mutex);
>
> + /*
> + * There are two control paths which try to determine cgroup from
> + * dentry without going through kernfs - cgroupstats_build() and
> + * css_tryget_online_from_dir(). Those are supported by RCU
> + * protecting clearing of cgrp->kn->priv backpointer.
> + */
> + if (!ss && cgroup_parent(cgrp))
> + RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv, NULL);
Can we move the above into the preceding else block? I don't think
holding cgroup_mutex or not makes any difference here. Also, why do
we need the cgroup_parent() check? Do we deref root's kn->priv in the
destruction path? If so, can you please note that in the comment?
Thanks.
--
tejun
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