diff options
Diffstat (limited to 'include/linux/cgroup.h')
| -rw-r--r-- | include/linux/cgroup.h | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index ee041a01a67e..d0ad3794b947 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -688,9 +688,9 @@ struct cgroup *cgroup_next_sibling(struct cgroup *pos); /** * cgroup_for_each_child - iterate through children of a cgroup * @pos: the cgroup * to use as the loop cursor - * @cgroup: cgroup whose children to walk + * @cgrp: cgroup whose children to walk * - * Walk @cgroup's children. Must be called under rcu_read_lock(). A child + * Walk @cgrp's children. Must be called under rcu_read_lock(). A child * cgroup which hasn't finished ->css_online() or already has finished * ->css_offline() may show up during traversal and it's each subsystem's * responsibility to verify that each @pos is alive. @@ -698,9 +698,15 @@ struct cgroup *cgroup_next_sibling(struct cgroup *pos); * If a subsystem synchronizes against the parent in its ->css_online() and * before starting iterating, a cgroup which finished ->css_online() is * guaranteed to be visible in the future iterations. + * + * It is allowed to temporarily drop RCU read lock during iteration. The + * caller is responsible for ensuring that @pos remains accessible until + * the start of the next iteration by, for example, bumping the css refcnt. */ -#define cgroup_for_each_child(pos, cgroup) \ - list_for_each_entry_rcu(pos, &(cgroup)->children, sibling) +#define cgroup_for_each_child(pos, cgrp) \ + for ((pos) = list_first_or_null_rcu(&(cgrp)->children, \ + struct cgroup, sibling); \ + (pos); (pos) = cgroup_next_sibling((pos))) struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos, struct cgroup *cgroup); @@ -759,6 +765,10 @@ struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos); * Alternatively, a subsystem may choose to use a single global lock to * synchronize ->css_online() and ->css_offline() against tree-walking * operations. + * + * It is allowed to temporarily drop RCU read lock during iteration. The + * caller is responsible for ensuring that @pos remains accessible until + * the start of the next iteration by, for example, bumping the css refcnt. */ #define cgroup_for_each_descendant_pre(pos, cgroup) \ for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos); \ |