Re: [PATCH] cgroups: fix probable race with put_css_set[_taskexit] and find_css_set

["Paul Menage" <menage@google.com>]

On Tue, Sep 9, 2008 at 7:18 PM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
>        hlist_for_each_entry(cg, node, hhead, hlist) {
>                if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) {
>                        /* All subsystems matched */
> +                       if (!kref_get_not_zero(&cg->ref))
> +                               return NULL;

Maybe it would be better to do:

if (!memcmp(...) && kref_get_not_zero(&cg->ref))
  return cg;

so that in the event of a race, we carry on looking in the array.
> + * Return 0 if this refcount is 0, otherwise return 1.
> + */
> +int kref_get_not_zero(struct kref *kref)

Probably clearer to have a bool return type.

Paul