From 3b281afbc3a06cd69c54e6db1a04a8e73997723f Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 23 Apr 2014 11:13:15 -0400 Subject: [PATCH] cgroup: make css_next_child() skip missing csses css_next_child() walks the children of the specified css. It does this by finding the next cgroup and then returning the requested css. On the default unified hierarchy, a cgroup may not have a css associated with it even if the hierarchy has the subsystem enabled. This patch updates css_next_child() so that it skips children without the requested css associated. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- kernel/cgroup.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 37d966289978..0edc186cd545 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2708,10 +2708,19 @@ css_next_child(struct cgroup_subsys_state *pos_css, break; } - if (&next->sibling == &cgrp->children) - return NULL; + /* + * @next, if not pointing to the head, can be dereferenced and is + * the next sibling; however, it might have @ss disabled. If so, + * fast-forward to the next enabled one. + */ + while (&next->sibling != &cgrp->children) { + struct cgroup_subsys_state *next_css = cgroup_css(next, parent_css->ss); - return cgroup_css(next, parent_css->ss); + if (next_css) + return next_css; + next = list_entry_rcu(next->sibling.next, struct cgroup, sibling); + } + return NULL; } /**