Applied the following patch to cgroup/for-4.18. Thanks.
------ 8< ------ >From d8742e22902186e30c346b1ba881cb52942ae3e4 Mon Sep 17 00:00:00 2001 From: Tejun Heo <[email protected]> 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 <[email protected]> Reported-by: Boqun Feng <[email protected]> --- 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
