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Commit 82d6489d authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Tejun Heo
Browse files

cgroup: Disable IRQs while holding css_set_lock 



While testing the deadline scheduler + cgroup setup I hit this
warning.

[  132.612935] ------------[ cut here ]------------
[  132.612951] WARNING: CPU: 5 PID: 0 at kernel/softirq.c:150 __local_bh_enable_ip+0x6b/0x80
[  132.612952] Modules linked in: (a ton of modules...)
[  132.612981] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 4.7.0-rc2 #2
[  132.612981] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.2-20150714_191134- 04/01/2014
[  132.612982]  0000000000000086 45c8bb5effdd088b ffff88013fd43da0 ffffffff813d229e
[  132.612984]  0000000000000000 0000000000000000 ffff88013fd43de0 ffffffff810a652b
[  132.612985]  00000096811387b5 0000000000000200 ffff8800bab29d80 ffff880034c54c00
[  132.612986] Call Trace:
[  132.612987]  <IRQ>  [<ffffffff813d229e>] dump_stack+0x63/0x85
[  132.612994]  [<ffffffff810a652b>] __warn+0xcb/0xf0
[  132.612997]  [<ffffffff810e76a0>] ? push_dl_task.part.32+0x170/0x170
[  132.612999]  [<ffffffff810a665d>] warn_slowpath_null+0x1d/0x20
[  132.613000]  [<ffffffff810aba5b>] __local_bh_enable_ip+0x6b/0x80
[  132.613008]  [<ffffffff817d6c8a>] _raw_write_unlock_bh+0x1a/0x20
[  132.613010]  [<ffffffff817d6c9e>] _raw_spin_unlock_bh+0xe/0x10
[  132.613015]  [<ffffffff811388ac>] put_css_set+0x5c/0x60
[  132.613016]  [<ffffffff8113dc7f>] cgroup_free+0x7f/0xa0
[  132.613017]  [<ffffffff810a3912>] __put_task_struct+0x42/0x140
[  132.613018]  [<ffffffff810e776a>] dl_task_timer+0xca/0x250
[  132.613027]  [<ffffffff810e76a0>] ? push_dl_task.part.32+0x170/0x170
[  132.613030]  [<ffffffff8111371e>] __hrtimer_run_queues+0xee/0x270
[  132.613031]  [<ffffffff81113ec8>] hrtimer_interrupt+0xa8/0x190
[  132.613034]  [<ffffffff81051a58>] local_apic_timer_interrupt+0x38/0x60
[  132.613035]  [<ffffffff817d9b0d>] smp_apic_timer_interrupt+0x3d/0x50
[  132.613037]  [<ffffffff817d7c5c>] apic_timer_interrupt+0x8c/0xa0
[  132.613038]  <EOI>  [<ffffffff81063466>] ? native_safe_halt+0x6/0x10
[  132.613043]  [<ffffffff81037a4e>] default_idle+0x1e/0xd0
[  132.613044]  [<ffffffff810381cf>] arch_cpu_idle+0xf/0x20
[  132.613046]  [<ffffffff810e8fda>] default_idle_call+0x2a/0x40
[  132.613047]  [<ffffffff810e92d7>] cpu_startup_entry+0x2e7/0x340
[  132.613048]  [<ffffffff81050235>] start_secondary+0x155/0x190
[  132.613049] ---[ end trace f91934d162ce9977 ]---

The warn is the spin_(lock|unlock)_bh(&css_set_lock) in the interrupt
context. Converting the spin_lock_bh to spin_lock_irq(save) to avoid
this problem - and other problems of sharing a spinlock with an
interrupt.

Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: cgroups@vger.kernel.org
Cc: stable@vger.kernel.org # 4.5+
Cc: linux-kernel@vger.kernel.org
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Reviewed-by: default avatar"Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: default avatarZefan Li <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 8fa3b8d6

kernel/cgroup.c

+74 −68
Original line number Diff line number Diff line
@@ -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)
@@ -5449,10 +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)
@@ -5723,7 +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;
@@ -5776,7 +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:
@@ -5921,13 +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);

	}



	/*
@@ -5972,9 +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);

	}
@@ -6042,9 +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;
@@ -6304,12 +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();
@@ -6433,7 +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) {
@@ -6444,7 +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;

}
@@ -6455,7 +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;
@@ -6478,7 +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;

}