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Subject[PATCH 4.4 33/77] cgroup: Disable IRQs while holding css_set_lock
Date
From: Daniel Bristot de Oliveira <bristot@redhat.com>

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@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: Rik van Riel <riel@redhat.com>
Reviewed-by: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Zubin Mithra <zsm@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/cgroup.c | 122 +++++++++++++++++++++++++++++---------------------------
1 file changed, 64 insertions(+), 58 deletions(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -784,6 +784,8 @@ 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
@@ -792,9 +794,9 @@ 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);
}

/*
@@ -1017,11 +1019,11 @@ 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;
@@ -1049,7 +1051,7 @@ 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;
@@ -1075,7 +1077,7 @@ 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;
}
@@ -1139,7 +1141,7 @@ 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);
@@ -1147,7 +1149,7 @@ 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);
@@ -1551,11 +1553,11 @@ 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);

src_root->subsys_mask &= ~(1 << ssid);
scgrp->subtree_control &= ~(1 << ssid);
@@ -1832,7 +1834,7 @@ 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;
@@ -1857,8 +1859,12 @@ 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);

@@ -1867,11 +1873,11 @@ 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)
@@ -1976,13 +1982,13 @@ 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);
@@ -2215,7 +2221,7 @@ 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);

@@ -2228,7 +2234,7 @@ 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;
}
@@ -2403,7 +2409,7 @@ 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);
@@ -2414,7 +2420,7 @@ 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.
@@ -2443,13 +2449,13 @@ out_cancel_attach:
}
}
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;
}

@@ -2466,14 +2472,14 @@ 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_cset = NULL;
list_del_init(&cset->mg_preload_node);
put_css_set_locked(cset);
}
- spin_unlock_bh(&css_set_lock);
+ spin_unlock_irq(&css_set_lock);
}

/**
@@ -2623,7 +2629,7 @@ 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 {
@@ -2632,7 +2638,7 @@ 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, cgrp);
}
@@ -2653,7 +2659,7 @@ static int cgroup_attach_task(struct cgr
int ret;

/* look up all src csets */
- spin_lock_bh(&css_set_lock);
+ spin_lock_irq(&css_set_lock);
rcu_read_lock();
task = leader;
do {
@@ -2663,7 +2669,7 @@ 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(dst_cgrp, &preloaded_csets);
@@ -2696,9 +2702,9 @@ 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);
@@ -2800,9 +2806,9 @@ 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)
@@ -2927,7 +2933,7 @@ 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);
css_for_each_descendant_pre(css, cgroup_css(cgrp, NULL)) {
struct cgrp_cset_link *link;

@@ -2939,14 +2945,14 @@ static int cgroup_update_dfl_csses(struc
cgroup_migrate_add_src(link->cset, cgrp,
&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(NULL, &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;

@@ -2958,7 +2964,7 @@ 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);
out_finish:
@@ -3641,10 +3647,10 @@ 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;
}

@@ -3982,7 +3988,7 @@ 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;

@@ -3995,7 +4001,7 @@ 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);
}

/**
@@ -4013,7 +4019,7 @@ 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,
@@ -4022,7 +4028,7 @@ 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;
}
@@ -4036,10 +4042,10 @@ 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)
@@ -4068,10 +4074,10 @@ 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(to, &preloaded_csets);
if (ret)
@@ -5180,10 +5186,10 @@ 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)
@@ -5436,7 +5442,7 @@ 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;
@@ -5488,7 +5494,7 @@ 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:
@@ -5649,13 +5655,13 @@ 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);
}

/*
@@ -5699,9 +5705,9 @@ 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);
}
@@ -5914,7 +5920,7 @@ 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) {
@@ -5925,7 +5931,7 @@ 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;
}
@@ -5936,7 +5942,7 @@ 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;
@@ -5959,7 +5965,7 @@ 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;
}


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