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cgroup: drop hierarchy_id_lock

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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 <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-04-14 11:36:57 -07:00
parent fa3ca07e96
commit 54e7b4eb15
1 changed files with 18 additions and 7 deletions
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25
kernel/cgroup.c
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@ -189,9 +189,13 @@ 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)
@ -1430,10 +1434,12 @@ 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);
@ -1446,18 +1452,17 @@ 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)
{
if (root->hierarchy_id) {
spin_lock(&hierarchy_id_lock);
ida_remove(&hierarchy_ida, root->hierarchy_id);
spin_unlock(&hierarchy_id_lock);
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&cgroup_root_mutex);
if (root->hierarchy_id) {
ida_remove(&hierarchy_ida, root->hierarchy_id);
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;