From 389b9c1bc927c8194a49f5f0c7e069ed0ec79b9e Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 15 Oct 2015 16:41:51 -0400
Subject: [PATCH] cgroup: keep css_set and task lists in chronological order
css task iteration will be updated to not leak cgroup internal locking
to iterator users. In preparation, update css_set and task lists to
be in chronological order.
For tasks, as migration path is already using list_splice_tail_init(),
only cgroup_enable_task_cg_lists() and cgroup_post_fork() need
updating. For css_sets, link_css_set() is the only place which needs
to be updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 61ee85ded6ae..52444673e9a2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -914,12 +914,11 @@ static void link_css_set(struct list_head *tmp_links, struct css_set *cset,
link->cset = cset;
link->cgrp = cgrp;
- list_move(&link->cset_link, &cgrp->cset_links);
-
/*
- * Always add links to the tail of the list so that the list
- * is sorted by order of hierarchy creation
+ * Always add links to the tail of the lists so that the lists are
+ * in choronological order.
*/
+ list_move_tail(&link->cset_link, &cgrp->cset_links);
list_add_tail(&link->cgrp_link, &cset->cgrp_links);
if (cgroup_parent(cgrp))
@@ -1780,7 +1779,7 @@ static void cgroup_enable_task_cg_lists(void)
if (!css_set_populated(cset))
css_set_update_populated(cset, true);
- list_add(&p->cg_list, &cset->tasks);
+ list_add_tail(&p->cg_list, &cset->tasks);
get_css_set(cset);
}
spin_unlock_irq(&p->sighand->siglock);
@@ -5480,7 +5479,7 @@ void cgroup_post_fork(struct task_struct *child,
cset = task_css_set(current);
if (list_empty(&child->cg_list)) {
rcu_assign_pointer(child->cgroups, cset);
- list_add(&child->cg_list, &cset->tasks);
+ list_add_tail(&child->cg_list, &cset->tasks);
get_css_set(cset);
}
up_write(&css_set_rwsem);