[ 1365.060340] rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { P2852 } 1202455 jiffies s: 10101 root: 0x0/T
[ 1365.060504] rcu: blocking rcu_node structures (internal RCU debug):
[ 1380.711331] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 1380.711457] rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-3): P2852/1:b..l
[ 1380.711533] rcu: 	(detected by 3, t=1218102 jiffies, g=23421, q=262 ncpus=4)
[ 1380.711598] task:grep            state:D stack:12736 pid:2852  tgid:2852  ppid:1      task_flags:0x40010c flags:0x00004002
[ 1380.711695] Call Trace:
[ 1380.711717]  <TASK>
[ 1380.711740]  __schedule+0x4e3/0xb40
[ 1380.711788]  schedule+0x27/0xd0
[ 1380.711826]  synchronize_rcu_expedited+0x17c/0x2f0
[ 1380.711880]  ? __pfx_autoremove_wake_function+0x10/0x10
[ 1380.711941]  ? __pfx_wait_rcu_exp_gp+0x10/0x10
[ 1380.711989]  namespace_unlock+0x20e/0x2e0
[ 1380.712030]  put_mnt_ns+0x68/0x80
[ 1380.712068]  free_nsproxy+0x16/0x190
[ 1380.712105]  do_exit+0x267/0xae0
[ 1380.712148]  ? ksys_read+0x65/0xe0
[ 1380.712195]  make_task_dead+0x7d/0x160
[ 1380.712226]  rewind_stack_and_make_dead+0x16/0x20
[ 1380.712281] RIP: 0033:0x7f29925e0292
[ 1380.712323] RSP: 002b:00007ffedfc826e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 1380.712414] RAX: ffffffffffffffda RBX: 0000000000018000 RCX: 00007f29925e0292
[ 1380.712504] RDX: 0000000000018000 RSI: 000055b99aadb000 RDI: 0000000000000005
[ 1380.712582] RBP: 000055b99aadb000 R08: 0000000000000003 R09: 0000000000000000
[ 1380.712644] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffedfc827c0
[ 1380.712709] R13: 0000000000000005 R14: 0000000000001000 R15: 0000000000000005
[ 1380.712775]  </TASK>