diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index b76999954beb5ffbb835cd66dc917a051fb194e2..4afe544d35479329d42d83ab757d6869eedf4693 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -112,6 +112,24 @@ static inline void css_get(struct cgroup_subsys_state *css) percpu_ref_get(&css->refcnt); } +/** + * css_tryget - try to obtain a reference on the specified css + * @css: target css + * + * Obtain a reference on @css unless it already has reached zero and is + * being released. This function doesn't care whether @css is on or + * offline. The caller naturally needs to ensure that @css is accessible + * but doesn't have to be holding a reference on it - IOW, RCU protected + * access is good enough for this function. Returns %true if a reference + * count was successfully obtained; %false otherwise. + */ +static inline bool css_tryget(struct cgroup_subsys_state *css) +{ + if (!(css->flags & CSS_NO_REF)) + return percpu_ref_tryget(&css->refcnt); + return true; +} + /** * css_tryget_online - try to obtain a reference on the specified css if online * @css: target css