diff options
Diffstat (limited to 'include/linux/cgroup.h')
| -rw-r--r-- | include/linux/cgroup.h | 27 |
1 files changed, 24 insertions, 3 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index c5648fcf74e2..f2aa46a4f871 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -640,11 +640,32 @@ static inline bool task_under_cgroup_hierarchy(struct task_struct *task, return cgroup_is_descendant(cset->dfl_cgrp, ancestor); } -/* no synchronization, the result can only be used as a hint */ +/* + * Populated counters: writes happen under css_set_lock. The accessors below + * may read unlocked. What an unpopulated result means depends on context: + * + * - No lock held. Just a snapshot. May race with concurrent updates and is + * useful only as a hint. + * + * - cgroup_mutex held. Migration into the cgroup is blocked, so an observed + * !populated stays !populated until cgroup_mutex is dropped. + * + * - CSS_DYING set. The css can no longer be repopulated, so !populated is + * sticky once observed. + */ +static inline bool cgroup_has_tasks(struct cgroup *cgrp) +{ + return READ_ONCE(cgrp->self.nr_populated_csets); +} + +static inline bool css_is_populated(struct cgroup_subsys_state *css) +{ + return READ_ONCE(css->nr_populated_csets) || READ_ONCE(css->nr_populated_children); +} + static inline bool cgroup_is_populated(struct cgroup *cgrp) { - return cgrp->nr_populated_csets + cgrp->nr_populated_domain_children + - cgrp->nr_populated_threaded_children; + return css_is_populated(&cgrp->self); } /* returns ino associated with a cgroup */ |