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authorLi Zefan <lizf@cn.fujitsu.com>2008-11-12 13:26:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-12 17:17:16 -0800
commit3b1b3f6e57064aa8f91c290fe51cda4c74642902 (patch)
tree2cf60a7bae5f184acbea4bff859be4e4132f9794 /kernel
parent687446760bd008df96655cb8c5900f8e48a7118c (diff)
downloadlinux-3b1b3f6e57064aa8f91c290fe51cda4c74642902.tar.bz2
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 <lizf@cn.fujitsu.com> Acked-by: Paul Menage <menage@google.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: Paul Menage <menage@google.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: "Serge E. Hallyn" <serue@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup_freezer.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 660590710409..fb249e2bcada 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));
}