[PATCH 4.6 50/96] cgroup: Disable IRQs while holding css_set_lock

From: Greg Kroah-Hartman
Date: Mon Aug 08 2016 - 15:31:07 EST

4.6-stable review patch. If anyone has any objections, please let me know.

------------------

From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

commit 82d6489d0fed2ec8a8c48c19e8d8a04ac8e5bb26 upstream.

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@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Reviewed-by: "Luis Claudio R. Goncalves" <lgoncalv@xxxxxxxxxx>
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Acked-by: Zefan Li <lizefan@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
kernel/cgroup.c | 142 +++++++++++++++++++++++++++++---------------------------
1 file changed, 74 insertions(+), 68 deletions(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -837,6 +837,8 @@ static void put_css_set_locked(struct cs

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 *
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(stru

/* 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(stru
* 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(stru
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 c
* 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 c
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 cgro
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_f
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(
{
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(
* 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(
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 cgro
* 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 @@ out_mount:
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 *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_struc
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_struc
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
* 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
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 @@ out_cancel_attach:
}
} 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

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_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_st
* 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_st
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 cgr
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 cgr
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 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_s
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(struc
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(struc
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(struc
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 struc
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_s

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_s

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(s
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(s
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(s
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
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
*/
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,
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,

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
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
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(
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
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
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
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
overflow:
seq_puts(seq, " ...\n");
}
- spin_unlock_bh(&css_set_lock);
+ spin_unlock_irq(&css_set_lock);
return 0;
}