Applied the following patch to cgroup/for-4.18.
Thanks.
------ 8< ------
>From d8742e22902186e30c346b1ba881cb52942ae3e4 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@xxxxxxxxxx>
Date: Wed, 23 May 2018 11:04:54 -0700
cgroup_enable_task_cg_lists() incorrectly nests non-irq-safe
tasklist_lock inside irq-safe css_set_lock triggering the following
lockdep warning.
WARNING: possible irq lock inversion dependency detected
4.17.0-rc1-00027-gb37d049 #6 Not tainted
--------------------------------------------------------
systemd/1 just changed the state of lock:
00000000fe57773b (css_set_lock){..-.}, at: cgroup_free+0xf2/0x12a
but this lock took another, SOFTIRQ-unsafe lock in the past:
(tasklist_lock){.+.+}
and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(tasklist_lock);
local_irq_disable();
lock(css_set_lock);
lock(tasklist_lock);
<Interrupt>
lock(css_set_lock);
*** DEADLOCK ***
The condition is highly unlikely to actually happen especially given
that the path is executed only once per boot.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Boqun Feng <boqun.feng@xxxxxxxxx>
---
kernel/cgroup/cgroup.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 04b7e7f..63989cb 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1798,13 +1798,6 @@ static void cgroup_enable_task_cg_lists(void)
{
struct task_struct *p, *g;
- spin_lock_irq(&css_set_lock);
-
- if (use_task_css_set_links)
- goto out_unlock;
-
- use_task_css_set_links = true;
-
/*
* We need tasklist_lock because RCU is not safe against
* while_each_thread(). Besides, a forking task that has passed
@@ -1813,6 +1806,13 @@ static void cgroup_enable_task_cg_lists(void)
* tasklist if we walk through it with RCU.
*/
read_lock(&tasklist_lock);
+ spin_lock_irq(&css_set_lock);
+
+ if (use_task_css_set_links)
+ goto out_unlock;
+
+ use_task_css_set_links = true;
+
do_each_thread(g, p) {
WARN_ON_ONCE(!list_empty(&p->cg_list) ||
task_css_set(p) != &init_css_set);
@@ -1840,9 +1840,9 @@ static void cgroup_enable_task_cg_lists(void)
}
spin_unlock(&p->sighand->siglock);
} while_each_thread(g, p);
- read_unlock(&tasklist_lock);
out_unlock:
spin_unlock_irq(&css_set_lock);
+ read_unlock(&tasklist_lock);
}
static void init_cgroup_housekeeping(struct cgroup *cgrp)
--
2.9.5
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