Now that hierarchy_id alloc / free are protected by the cgroup
mutexes, there's no need for this separate lock. Drop it.
Signed-off-by: Tejun Heo <t...@kernel.org>
---
kernel/cgroup.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 823cb56..e15bdb7 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -237,9 +237,13 @@ struct cgroup_event {
static LIST_HEAD(roots);
static int root_count;
+/*
+ * Hierarchy ID allocation and mapping. It follows the same exclusion
+ * rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
+ * writes, either for reads.
+ */
static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
-static DEFINE_SPINLOCK(hierarchy_id_lock);
/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)
@@ -1456,10 +1460,12 @@ static int cgroup_init_root_id(struct cgroupfs_root
*root)
{
int ret;
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&cgroup_root_mutex);
+
do {
if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
return -ENOMEM;
- spin_lock(&hierarchy_id_lock);
/* Try to allocate the next unused ID */
ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
&root->hierarchy_id);
@@ -1472,18 +1478,17 @@ static int cgroup_init_root_id(struct cgroupfs_root
*root)
/* Can only get here if the 31-bit IDR is full ... */
BUG_ON(ret);
}
- spin_unlock(&hierarchy_id_lock);
} while (ret);
return 0;
}
static void cgroup_exit_root_id(struct cgroupfs_root *root)
{
+ lockdep_assert_held(&cgroup_mutex);
+ lockdep_assert_held(&cgroup_root_mutex);
+
if (root->hierarchy_id) {
- spin_lock(&hierarchy_id_lock);
ida_remove(&hierarchy_ida, root->hierarchy_id);
- spin_unlock(&hierarchy_id_lock);
-
root->hierarchy_id = 0;
}
}
@@ -4656,8 +4661,14 @@ int __init cgroup_init(void)
hash_add(css_set_table, &init_css_set.hlist, key);
/* allocate id for the dummy hierarchy */
+ mutex_lock(&cgroup_mutex);
+ mutex_lock(&cgroup_root_mutex);
+
BUG_ON(cgroup_init_root_id(&rootnode));
+ mutex_unlock(&cgroup_root_mutex);
+ mutex_unlock(&cgroup_mutex);
+
cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
if (!cgroup_kobj) {
err = -ENOMEM;
--
1.8.1.4
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