syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P324
	(detected by 1, t=10503 jiffies, g=7225, q=365)
kworker/u4:4    R  running task    26096   324      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:free_thread_stack+0x18b/0x590 kernel/fork.c:284
Code: ff ff e8 28 04 00 00 43 80 3c 2e 00 74 08 4c 89 e7 e8 39 94 6a 00 49 8b 1c 24 48 83 c3 08 48 89 d8 48 c1 e8 03 42 80 3c 28 00 <74> 08 48 89 df e8 1b 94 6a 00 48 8b 1b e9 82 ff ff ff e8 be 2b 2e
RSP: 0018:ffffc90001fd79c8 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: 1ffff110152c9c91 RBX: ffff8880a964e488 RCX: ffff8880a93c0400
RDX: 0000000000000000 RSI: 00000000fffffffc RDI: ffffea0002a4fc00
RBP: ffffc90001fd7a00 R08: dffffc0000000000 R09: fffffbfff124248a
R10: fffffbfff124248a R11: 0000000000000000 R12: ffff8880a964e520
R13: dffffc0000000000 R14: 1ffff110152c9ca4 R15: ffff888090a25838
 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:__rcu_read_unlock+0x37/0x6b0 kernel/rcu/tree_plugin.h:376
Code: 48 83 ec 28 49 be 00 00 00 00 00 fc ff df 65 4c 8b 3c 25 c0 1d 02 00 4d 8d a7 78 03 00 00 4d 89 e5 49 c1 ed 03 43 8a 44 35 00 <84> c0 0f 85 93 00 00 00 41 8b 1c 24 83 fb 01 75 54 4c 89 fa 43 8a
RSP: 0018:ffffc90001fd7c18 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffff13
RAX: ffffffff87e2bb00 RBX: ffff88809bc88000 RCX: ffff8880a93c0400
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880aea37e20
RBP: ffffc90001fd7c68 R08: dffffc0000000000 R09: ffffed1015d46fc5
R10: ffffed1015d46fc5 R11: 0000000000000000 R12: ffff8880a93c0778
R13: 1ffff110152780ef R14: dffffc0000000000 R15: ffff8880a93c0400
 rcu_read_unlock include/linux/rcupdate.h:670 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline]
 batadv_nc_worker+0x275/0x600 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 10533 jiffies! g7225 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I29032    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