---
 kernel/cgroup.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -779,6 +779,22 @@ static inline void get_css_set(struct cs
 	atomic_inc(&cset->refcount);
 }
 
+static void dump_cset(struct css_set *cset)
+{
+	struct cgrp_cset_link *link;
+
+	printk("XXX dumping cset %p\n", cset);
+	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
+		struct cgroup *cgrp = link->cgrp;
+		struct cgroup_root *root = cgrp->root;
+
+		printk("root %d:0x%04x:%s ",
+		       root->hierarchy_id, root->subsys_mask, root->name);
+		pr_cont_cgroup_path(cgrp);
+		pr_cont("\n");
+	}
+}
+
 /**
  * compare_css_sets - helper function for find_existing_css_set().
  * @cset: candidate css_set being tested
@@ -831,7 +847,10 @@ static bool compare_css_sets(struct css_
 		cgrp1 = link1->cgrp;
 		cgrp2 = link2->cgrp;
 		/* Hierarchies should be linked in the same order. */
-		BUG_ON(cgrp1->root != cgrp2->root);
+		if (WARN_ON(cgrp1->root != cgrp2->root)) {
+			dump_cset(cset);
+			dump_cset(old_cset);
+		}
 
 		/*
 		 * If this hierarchy is the hierarchy of the cgroup