Re: [PATCH 3.4 1/2] cgroup: Take css_set_lock when calling cgroup_css_sets_empty()

[Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Hi,

Self-nack, looks like I posted this series too soon. With a config which actually
has CGROUP controllers enabled this causes a panic, so looks like I need to do some
more work on this.

Feedback on this issue is still appreciated.

Regards,

Hans


On 01/09/2013 01:11 PM, Hans de Goede wrote:
> As indicated in the comment above cgroup_css_sets_empty the
> css_set_lock must be hold when calling it.
>
> Signed-off-by: Hans de Goede <hdegoede-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
>   kernel/cgroup.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index c908354..59e711a 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -3980,7 +3980,10 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
>   	/* the vfs holds both inode->i_mutex already */
>   again:
>   	mutex_lock(&cgroup_mutex);
> -	if (!cgroup_css_sets_empty(cgrp)) {
> +	read_lock(&css_set_lock);
> +	ret = cgroup_css_sets_empty(cgrp);
> +	read_unlock(&css_set_lock);
> +	if (!ret) {
>   		mutex_unlock(&cgroup_mutex);
>   		return -EBUSY;
>   	}
>