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Commit 54e7b4eb authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: drop hierarchy_id_lock 



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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent fa3ca07e

kernel/cgroup.c

+17 −6
Original line number Diff line number Diff line
@@ -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)

{

	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;