syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P120
	(detected by 0, t=10503 jiffies, g=6709, q=181)
kworker/u4:3    R  running task    25720   120      2 0x80004008
Workqueue: bat_events batadv_nc_worker
Call Trace:
 <IRQ>
 sched_show_task+0x40f/0x560 kernel/sched/core.c:5954
 rcu_print_detail_task_stall_rnp kernel/rcu/tree_stall.h:190 [inline]
 print_other_cpu_stall kernel/rcu/tree_stall.h:398 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:538 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0x16b1/0x1ad0 kernel/rcu/tree.c:2271
 update_process_times+0x12d/0x180 kernel/time/timer.c:1726
 tick_sched_handle kernel/time/tick-sched.c:167 [inline]
 tick_sched_timer+0x263/0x420 kernel/time/tick-sched.c:1310
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x403/0x840 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x38c/0xda0 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0x109/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 </IRQ>
RIP: 0010:__memcg_kmem_uncharge+0x21/0x1a0 mm/memcontrol.c:2910
Code: 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 41 57 41 56 41 55 41 54 53 50 89 f3 49 89 fc 48 b8 00 00 00 00 00 fc ff df 4c 8d 77 38 <4d> 89 f5 49 c1 ed 03 41 80 7c 05 00 00 74 08 4c 89 f7 e8 78 fe fa
RSP: 0018:ffffc900012f7968 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffff8880a94ee3c0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffea00029e8600
RBP: ffffc900012f7998 R08: 000000000003a728 R09: ffffed101504aa9f
R10: ffffed101504aa9f R11: 0000000000000000 R12: ffffea00029e8600
R13: dffffc0000000000 R14: ffffea00029e8638 R15: ffff8880a82554e8
 memcg_kmem_uncharge include/linux/memcontrol.h:1402 [inline]
 free_thread_stack+0x12e/0x590 kernel/fork.c:284
 release_task_stack kernel/fork.c:440 [inline]
 put_task_stack+0xa3/0x130 kernel/fork.c:451
 finish_task_switch+0x3f1/0x550 kernel/sched/core.c:3256
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x9a8/0xcc0 kernel/sched/core.c:4081
 preempt_schedule_irq+0xc1/0x140 kernel/sched/core.c:4338
 retint_kernel+0x1b/0x2b
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
RIP: 0010:lock_acquire+0x1b2/0x250 kernel/locking/lockdep.c:4488
Code: c1 e8 03 42 80 3c 30 00 74 0c 48 c7 c7 28 95 0a 89 e8 42 7c 56 00 48 83 3d 62 02 af 07 00 0f 84 9c 00 00 00 48 8b 7d c0 57 9d <0f> 1f 44 00 00 48 83 c4 30 5b 41 5c 41 5d 41 5e 41 5f 5d c3 44 89
RSP: 0018:ffffc900012f7bf8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff02
RAX: 1ffffffff12152a5 RBX: 0000000000000000 RCX: e8e544b044cba3c3
RDX: dffffc0000000000 RSI: ffff8880a94eeca8 RDI: 0000000000000286
RBP: ffffc900012f7c50 R08: dffffc0000000000 R09: fffffbfff13ca11d
R10: fffffbfff13ca11d R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: ffffffff890d4ac0
 rcu_lock_acquire+0x2e/0x40 include/linux/rcupdate.h:208
 rcu_read_lock include/linux/rcupdate.h:617 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:407 [inline]
 batadv_nc_worker+0xdc/0x600 net/batman-adv/network-coding.c:718
 process_one_work+0x7ef/0x10d0 kernel/workqueue.c:2264
 worker_thread+0xc01/0x1630 kernel/workqueue.c:2410
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
rcu: rcu_preempt kthread starved for 10448 jiffies! g6709 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    29032    10      2 0x80004000
Call Trace:
 context_switch kernel/sched/core.c:3385 [inline]
 __schedule+0x9a0/0xcc0 kernel/sched/core.c:4081
 schedule+0x181/0x210 kernel/sched/core.c:4155
 schedule_timeout+0x14f/0x240 kernel/time/timer.c:1895
 rcu_gp_fqs_loop kernel/rcu/tree.c:1661 [inline]
 rcu_gp_kthread+0xed8/0x1770 kernel/rcu/tree.c:1821
 kthread+0x332/0x350 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352