Merge branch 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:
 "Three fix patches.  Two are for cgroup / css init failure path.  The
  last one makes css_set_lock irq-safe as the deadline scheduler ends up
  calling put_css_set() from irq context"

* 'for-4.7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Disable IRQs while holding css_set_lock
  cgroup: set css->id to -1 during init
  cgroup: remove redundant cleanup in css_create

kernel/cgroup.c

@@ -837,6 +837,8 @@ static void put_css_set_locked(struct css_set *cset)
 
 static void put_css_set(struct css_set *cset)
 {
+	unsigned long flags;
+
 	/*
 	 * Ensure that the refcount doesn't hit zero while any readers
 	 * can see it. Similar to atomic_dec_and_lock(), but for an
@@ -845,9 +847,9 @@ static void put_css_set(struct css_set *cset)
 	if (atomic_add_unless(&cset->refcount, -1, 1))
 		return;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irqsave(&css_set_lock, flags);
 	put_css_set_locked(cset);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irqrestore(&css_set_lock, flags);
 }
 
 /*
@@ -1070,11 +1072,11 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 
 	/* First see if we already have a cgroup group that matches
 	 * the desired set */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	cset = find_existing_css_set(old_cset, cgrp, template);
 	if (cset)
 		get_css_set(cset);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	if (cset)
 		return cset;
@@ -1102,7 +1104,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 	 * find_existing_css_set() */
 	memcpy(cset->subsys, template, sizeof(cset->subsys));
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	/* Add reference counts and links from the new css_set. */
 	list_for_each_entry(link, &old_cset->cgrp_links, cgrp_link) {
 		struct cgroup *c = link->cgrp;
@@ -1128,7 +1130,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
 		css_get(css);
 	}
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	return cset;
 }
@@ -1192,7 +1194,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 	 * Release all the links from cset_links to this hierarchy's
 	 * root cgroup
 	 */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
 		list_del(&link->cset_link);
@@ -1200,7 +1202,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 		kfree(link);
 	}
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	if (!list_empty(&root->root_list)) {
 		list_del(&root->root_list);
@@ -1600,11 +1602,11 @@ static int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask)
 		ss->root = dst_root;
 		css->cgroup = dcgrp;
 
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		hash_for_each(css_set_table, i, cset, hlist)
 			list_move_tail(&cset->e_cset_node[ss->id],
 				       &dcgrp->e_csets[ss->id]);
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 
 		/* default hierarchy doesn't enable controllers by default */
 		dst_root->subsys_mask |= 1 << ssid;
@@ -1640,10 +1642,10 @@ static int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
 	if (!buf)
 		return -ENOMEM;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	ns_cgroup = current_cgns_cgroup_from_root(kf_cgroot);
 	len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	if (len >= PATH_MAX)
 		len = -ERANGE;
@@ -1897,7 +1899,7 @@ static void cgroup_enable_task_cg_lists(void)
 {
 	struct task_struct *p, *g;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	if (use_task_css_set_links)
 		goto out_unlock;
@@ -1922,8 +1924,12 @@ static void cgroup_enable_task_cg_lists(void)
 		 * entry won't be deleted though the process has exited.
 		 * Do it while holding siglock so that we don't end up
 		 * racing against cgroup_exit().
+		 *
+		 * Interrupts were already disabled while acquiring
+		 * the css_set_lock, so we do not need to disable it
+		 * again when acquiring the sighand->siglock here.
 		 */
-		spin_lock_irq(&p->sighand->siglock);
+		spin_lock(&p->sighand->siglock);
 		if (!(p->flags & PF_EXITING)) {
 			struct css_set *cset = task_css_set(p);
 
@@ -1932,11 +1938,11 @@ static void cgroup_enable_task_cg_lists(void)
 			list_add_tail(&p->cg_list, &cset->tasks);
 			get_css_set(cset);
 		}
-		spin_unlock_irq(&p->sighand->siglock);
+		spin_unlock(&p->sighand->siglock);
 	} while_each_thread(g, p);
 	read_unlock(&tasklist_lock);
 out_unlock:
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 }
 
 static void init_cgroup_housekeeping(struct cgroup *cgrp)
@@ -2043,13 +2049,13 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	 * Link the root cgroup in this hierarchy into all the css_set
 	 * objects.
 	 */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	hash_for_each(css_set_table, i, cset, hlist) {
 		link_css_set(&tmp_links, cset, root_cgrp);
 		if (css_set_populated(cset))
 			cgroup_update_populated(root_cgrp, true);
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	BUG_ON(!list_empty(&root_cgrp->self.children));
 	BUG_ON(atomic_read(&root->nr_cgrps) != 1);
@@ -2256,11 +2262,11 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
 		struct cgroup *cgrp;
 
 		mutex_lock(&cgroup_mutex);
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 
 		cgrp = cset_cgroup_from_root(ns->root_cset, root);
 
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 		mutex_unlock(&cgroup_mutex);
 
 		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
@@ -2337,11 +2343,11 @@ char *cgroup_path_ns(struct cgroup *cgrp, char *buf, size_t buflen,
 	char *ret;
 
 	mutex_lock(&cgroup_mutex);
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	ret = cgroup_path_ns_locked(cgrp, buf, buflen, ns);
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	mutex_unlock(&cgroup_mutex);
 
 	return ret;
@@ -2369,7 +2375,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
 	char *path = NULL;
 
 	mutex_lock(&cgroup_mutex);
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
 
@@ -2382,7 +2388,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
 			path = buf;
 	}
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	mutex_unlock(&cgroup_mutex);
 	return path;
 }
@@ -2557,7 +2563,7 @@ static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
 	 * the new cgroup.  There are no failure cases after here, so this
 	 * is the commit point.
 	 */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(cset, &tset->src_csets, mg_node) {
 		list_for_each_entry_safe(task, tmp_task, &cset->mg_tasks, cg_list) {
 			struct css_set *from_cset = task_css_set(task);
@@ -2568,7 +2574,7 @@ static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
 			put_css_set_locked(from_cset);
 		}
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	/*
 	 * Migration is committed, all target tasks are now on dst_csets.
@@ -2597,13 +2603,13 @@ static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
 		}
 	} while_each_subsys_mask();
 out_release_tset:
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_splice_init(&tset->dst_csets, &tset->src_csets);
 	list_for_each_entry_safe(cset, tmp_cset, &tset->src_csets, mg_node) {
 		list_splice_tail_init(&cset->mg_tasks, &cset->tasks);
 		list_del_init(&cset->mg_node);
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	return ret;
 }
 
@@ -2634,7 +2640,7 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets)
 
 	lockdep_assert_held(&cgroup_mutex);
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry_safe(cset, tmp_cset, preloaded_csets, mg_preload_node) {
 		cset->mg_src_cgrp = NULL;
 		cset->mg_dst_cgrp = NULL;
@@ -2642,7 +2648,7 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets)
 		list_del_init(&cset->mg_preload_node);
 		put_css_set_locked(cset);
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 }
 
 /**
@@ -2783,7 +2789,7 @@ static int cgroup_migrate(struct task_struct *leader, bool threadgroup,
 	 * already PF_EXITING could be freed from underneath us unless we
 	 * take an rcu_read_lock.
 	 */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	rcu_read_lock();
 	task = leader;
 	do {
@@ -2792,7 +2798,7 @@ static int cgroup_migrate(struct task_struct *leader, bool threadgroup,
 			break;
 	} while_each_thread(leader, task);
 	rcu_read_unlock();
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	return cgroup_taskset_migrate(&tset, root);
 }
@@ -2816,7 +2822,7 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
 		return -EBUSY;
 
 	/* look up all src csets */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	rcu_read_lock();
 	task = leader;
 	do {
@@ -2826,7 +2832,7 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
 			break;
 	} while_each_thread(leader, task);
 	rcu_read_unlock();
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	/* prepare dst csets and commit */
 	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
@@ -2859,9 +2865,9 @@ static int cgroup_procs_write_permission(struct task_struct *task,
 		struct cgroup *cgrp;
 		struct inode *inode;
 
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 
 		while (!cgroup_is_descendant(dst_cgrp, cgrp))
 			cgrp = cgroup_parent(cgrp);
@@ -2962,9 +2968,9 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
 		if (root == &cgrp_dfl_root)
 			continue;
 
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		from_cgrp = task_cgroup_from_root(from, root);
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 
 		retval = cgroup_attach_task(from_cgrp, tsk, false);
 		if (retval)
@@ -3080,7 +3086,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
 	percpu_down_write(&cgroup_threadgroup_rwsem);
 
 	/* look up all csses currently attached to @cgrp's subtree */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	cgroup_for_each_live_descendant_pre(dsct, d_css, cgrp) {
 		struct cgrp_cset_link *link;
 
@@ -3088,14 +3094,14 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
 			cgroup_migrate_add_src(link->cset, dsct,
 					       &preloaded_csets);
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	/* NULL dst indicates self on default hierarchy */
 	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
 	if (ret)
 		goto out_finish;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(src_cset, &preloaded_csets, mg_preload_node) {
 		struct task_struct *task, *ntask;
 
@@ -3107,7 +3113,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
 		list_for_each_entry_safe(task, ntask, &src_cset->tasks, cg_list)
 			cgroup_taskset_add(task, &tset);
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	ret = cgroup_taskset_migrate(&tset, cgrp->root);
 out_finish:
@@ -3908,10 +3914,10 @@ static int cgroup_task_count(const struct cgroup *cgrp)
 	int count = 0;
 	struct cgrp_cset_link *link;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(link, &cgrp->cset_links, cset_link)
 		count += atomic_read(&link->cset->refcount);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	return count;
 }
 
@@ -4249,7 +4255,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css,
 
 	memset(it, 0, sizeof(*it));
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	it->ss = css->ss;
 
@@ -4262,7 +4268,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css,
 
 	css_task_iter_advance_css_set(it);
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 }
 
 /**
@@ -4280,7 +4286,7 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
 		it->cur_task = NULL;
 	}
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	if (it->task_pos) {
 		it->cur_task = list_entry(it->task_pos, struct task_struct,
@@ -4289,7 +4295,7 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
 		css_task_iter_advance(it);
 	}
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	return it->cur_task;
 }
@@ -4303,10 +4309,10 @@ struct task_struct *css_task_iter_next(struct css_task_iter *it)
 void css_task_iter_end(struct css_task_iter *it)
 {
 	if (it->cur_cset) {
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		list_del(&it->iters_node);
 		put_css_set_locked(it->cur_cset);
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 	}
 
 	if (it->cur_task)
@@ -4338,10 +4344,10 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 	mutex_lock(&cgroup_mutex);
 
 	/* all tasks in @from are being moved, all csets are source */
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(link, &from->cset_links, cset_link)
 		cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	ret = cgroup_migrate_prepare_dst(&preloaded_csets);
 	if (ret)
@@ -5063,6 +5069,7 @@ static void init_and_link_css(struct cgroup_subsys_state *css,
 	memset(css, 0, sizeof(*css));
 	css->cgroup = cgrp;
 	css->ss = ss;
+	css->id = -1;
 	INIT_LIST_HEAD(&css->sibling);
 	INIT_LIST_HEAD(&css->children);
 	css->serial_nr = css_serial_nr_next++;
@@ -5150,7 +5157,7 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
 
 	err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
 	if (err < 0)
-		goto err_free_percpu_ref;
+		goto err_free_css;
 	css->id = err;
 
 	/* @css is ready to be brought online now, make it visible */
@@ -5174,9 +5181,6 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
 
 err_list_del:
 	list_del_rcu(&css->sibling);
-	cgroup_idr_remove(&ss->css_idr, css->id);
-err_free_percpu_ref:
-	percpu_ref_exit(&css->refcnt);
 err_free_css:
 	call_rcu(&css->rcu_head, css_free_rcu_fn);
 	return ERR_PTR(err);
@@ -5451,10 +5455,10 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 	 */
 	cgrp->self.flags &= ~CSS_ONLINE;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(link, &cgrp->cset_links, cset_link)
 		link->cset->dead = true;
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 
 	/* initiate massacre of all css's */
 	for_each_css(css, ssid, cgrp)
@@ -5725,7 +5729,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
 		goto out;
 
 	mutex_lock(&cgroup_mutex);
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	for_each_root(root) {
 		struct cgroup_subsys *ss;
@@ -5778,7 +5782,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
 
 	retval = 0;
 out_unlock:
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	mutex_unlock(&cgroup_mutex);
 	kfree(buf);
 out:
@@ -5923,13 +5927,13 @@ void cgroup_post_fork(struct task_struct *child)
 	if (use_task_css_set_links) {
 		struct css_set *cset;
 
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		cset = task_css_set(current);
 		if (list_empty(&child->cg_list)) {
 			get_css_set(cset);
 			css_set_move_task(child, NULL, cset, false);
 		}
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 	}
 
 	/*
@@ -5974,9 +5978,9 @@ void cgroup_exit(struct task_struct *tsk)
 	cset = task_css_set(tsk);
 
 	if (!list_empty(&tsk->cg_list)) {
-		spin_lock_bh(&css_set_lock);
+		spin_lock_irq(&css_set_lock);
 		css_set_move_task(tsk, cset, NULL, false);
-		spin_unlock_bh(&css_set_lock);
+		spin_unlock_irq(&css_set_lock);
 	} else {
 		get_css_set(cset);
 	}
@@ -6044,9 +6048,9 @@ static void cgroup_release_agent(struct work_struct *work)
 	if (!pathbuf || !agentbuf)
 		goto out;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	path = cgroup_path_ns_locked(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	if (!path)
 		goto out;
 
@@ -6306,12 +6310,12 @@ struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
 		return ERR_PTR(-EPERM);
 
 	mutex_lock(&cgroup_mutex);
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 
 	cset = task_css_set(current);
 	get_css_set(cset);
 
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	mutex_unlock(&cgroup_mutex);
 
 	new_ns = alloc_cgroup_ns();
@@ -6435,7 +6439,7 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
 	if (!name_buf)
 		return -ENOMEM;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	rcu_read_lock();
 	cset = rcu_dereference(current->cgroups);
 	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
@@ -6446,7 +6450,7 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
 			   c->root->hierarchy_id, name_buf);
 	}
 	rcu_read_unlock();
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	kfree(name_buf);
 	return 0;
 }
@@ -6457,7 +6461,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
 	struct cgroup_subsys_state *css = seq_css(seq);
 	struct cgrp_cset_link *link;
 
-	spin_lock_bh(&css_set_lock);
+	spin_lock_irq(&css_set_lock);
 	list_for_each_entry(link, &css->cgroup->cset_links, cset_link) {
 		struct css_set *cset = link->cset;
 		struct task_struct *task;
@@ -6480,7 +6484,7 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
 	overflow:
 		seq_puts(seq, "  ...\n");
 	}
-	spin_unlock_bh(&css_set_lock);
+	spin_unlock_irq(&css_set_lock);
 	return 0;
 }