From 3b1b3f6e57064aa8f91c290fe51cda4c74642902 Mon Sep 17 00:00:00 2001 From: Li Zefan Date: Wed, 12 Nov 2008 13:26:50 -0800 Subject: freezer_cg: disable writing freezer.state of root cgroup With this change, control file 'freezer.state' doesn't exist in root cgroup, making root cgroup unfreezable. I think it's reasonable to disallow freeze tasks in the root cgroup. And then we can avoid fork overhead when freezer subsystem is compiled but not used. Also make writing invalid value to freezer.state returns EINVAL rather than EIO. This is more consistent with other cgroup subsystem. Signed-off-by: Li Zefan Acked-by: Paul Menage Cc: Cedric Le Goater Cc: Paul Menage Cc: Matt Helsley Cc: "Serge E. Hallyn" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/cgroup_freezer.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 66059071040..fb249e2bcad 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -192,6 +192,13 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) */ freezer = task_freezer(task); + /* + * The root cgroup is non-freezable, so we can skip the + * following check. + */ + if (!freezer->css.cgroup->parent) + return; + spin_lock_irq(&freezer->lock); BUG_ON(freezer->state == CGROUP_FROZEN); @@ -335,7 +342,7 @@ static int freezer_write(struct cgroup *cgroup, else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0) goal_state = CGROUP_FROZEN; else - return -EIO; + return -EINVAL; if (!cgroup_lock_live_group(cgroup)) return -ENODEV; @@ -354,6 +361,8 @@ static struct cftype files[] = { static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup) { + if (!cgroup->parent) + return 0; return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files)); } -- cgit v1.2.3