rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P28/2:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=67989, q=3183 ncpus=2)
task:rcuc/1          state:R  running task     stack:23384 pid:28    tgid:28    ppid:2      task_flags:0x4208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5388 [inline]
 __schedule+0x16ec/0x5620 kernel/sched/core.c:7189
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7513
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:547 [inline]
 irqentry_exit+0x14f/0x760 kernel/entry/common.c:164
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pcpu_memcg_free_hook mm/percpu.c:-1 [inline]
RIP: 0010:free_percpu+0x2ba/0xf30 mm/percpu.c:2261
Code: 7b 09 00 00 44 89 f1 c1 f9 02 48 63 c9 48 8d 1c c8 49 89 dc 49 c1 ec 03 41 80 3c 2c 00 74 08 48 89 df e8 99 49 1e 00 48 8b 03 <48> 89 04 24 48 85 c0 0f 84 f7 00 00 00 48 89 e8 49 63 ed 41 80 3c
RSP: 0000:ffffc90000a2fb58 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffc900010b5b40 RCX: 0000000000016968
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200016a9a6 R12: 1ffff92000216b68
R13: 0000000000000008 R14: 000000000005a5a0 R15: ffff88801f6da000
 free_vfsmnt fs/namespace.c:729 [inline]
 delayed_free_vfsmnt+0x81/0xa0 fs/namespace.c:736
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core kernel/rcu/tree.c:2869 [inline]
 rcu_cpu_kthread+0x99e/0x1470 kernel/rcu/tree.c:2957
 smpboot_thread_fn+0x541/0xa50 kernel/smpboot.c:160
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>