diff options
author | Tejun Heo <tj@kernel.org> | 2018-05-23 11:04:54 -0700 |
---|---|---|
committer | Tejun Heo <tj@kernel.org> | 2018-05-23 11:04:54 -0700 |
commit | d8742e22902186e30c346b1ba881cb52942ae3e4 (patch) | |
tree | a4dd3d558a5eb43dd5ce547ec10a00e9c9bc993a /kernel/cgroup | |
parent | cc659e76f375ab158fb682c1e39b2a22bf9f7657 (diff) | |
download | linux-d8742e22902186e30c346b1ba881cb52942ae3e4.tar.bz2 |
cgroup: css_set_lock should nest inside tasklist_lock
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@kernel.org>
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r-- | kernel/cgroup/cgroup.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 04b7e7fad31a..63989cb44566 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) |