syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (10495 ticks this GP) idle=816/1/0x4000000000000000 softirq=9274/9274 fqs=0 
	(t=10502 jiffies g=8813 q=46)
rcu: rcu_preempt kthread starved for 10503 jiffies! g8813 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
rcu_preempt     I29112    10      2 0x00004000
Call Trace:
 context_switch kernel/sched/core.c:3458 [inline]
 __schedule+0x8ea/0x2210 kernel/sched/core.c:4219
 schedule+0xd0/0x2a0 kernel/sched/core.c:4294
 schedule_timeout+0x148/0x250 kernel/time/timer.c:1908
 rcu_gp_fqs_loop kernel/rcu/tree.c:1874 [inline]
 rcu_gp_kthread+0xae5/0x1b50 kernel/rcu/tree.c:2044
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
NMI backtrace for cpu 1
CPU: 1 PID: 6808 Comm: syz-executor429 Not tainted 5.8.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 nmi_cpu_backtrace.cold+0x70/0xb1 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b3/0x223 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x194/0x1cf kernel/rcu/tree_stall.h:320
 print_cpu_stall kernel/rcu/tree_stall.h:553 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:627 [inline]
 rcu_pending kernel/rcu/tree.c:3489 [inline]
 rcu_sched_clock_irq.cold+0x5b3/0xccc kernel/rcu/tree.c:2504
 update_process_times+0x25/0x60 kernel/time/timer.c:1737
 tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:176
 tick_sched_timer+0x108/0x290 kernel/time/tick-sched.c:1320
 __run_hrtimer kernel/time/hrtimer.c:1520 [inline]
 __hrtimer_run_queues+0x1d5/0xfc0 kernel/time/hrtimer.c:1584
 hrtimer_interrupt+0x32a/0x930 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0x142/0x5e0 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 </IRQ>
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0xe0/0x120 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
RIP: 0010:lock_acquire+0x270/0xad0 kernel/locking/lockdep.c:4962
Code: 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 f8 06 00 00 48 83 3d 45 d1 5a 08 00 0f 84 a6 05 00 00 48 8b 7c 24 08 57 9d <0f> 1f 44 00 00 48 b8 00 00 00 00 00 fc ff df 48 03 44 24 10 48 c7
RSP: 0018:ffffc900010c6cb0 EFLAGS: 00000282
RAX: 1ffffffff1369c11 RBX: ffff8880957f2180 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: 0000000000000008 RDI: 0000000000000282
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8c59aadf
R10: fffffbfff18b355b R11: 0000000000000000 R12: 0000000000000000
R13: ffff88808de00818 R14: 0000000000000000 R15: ffff8880957f2180
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
 _raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:175
 spin_lock_bh include/linux/spinlock.h:358 [inline]
 batadv_tt_local_purge_pending_clients+0x119/0x460 net/batman-adv/translation-table.c:3895
 batadv_tt_local_resize_to_mtu+0x96/0x130 net/batman-adv/translation-table.c:4198
 batadv_hardif_activate_interface.part.0.cold+0x14c/0x1ba net/batman-adv/hard-interface.c:653
 batadv_hardif_activate_interface net/batman-adv/hard-interface.c:800 [inline]
 batadv_hardif_enable_interface+0xa7d/0xb10 net/batman-adv/hard-interface.c:792
 batadv_softif_slave_add+0x92/0x150 net/batman-adv/soft-interface.c:892
 do_set_master+0x1c8/0x220 net/core/rtnetlink.c:2476
 do_setlink+0x903/0x35c0 net/core/rtnetlink.c:2611
 __rtnl_newlink+0xc21/0x1750 net/core/rtnetlink.c:3272
 rtnl_newlink+0x64/0xa0 net/core/rtnetlink.c:3398
 rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5461
 netlink_rcv_skb+0x15a/0x430 net/netlink/af_netlink.c:2469
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x856/0xd90 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:672
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2352
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2406
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2439
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x4437d9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb 0f fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe88a73de8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000004437d9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000004
RBP: 00007ffe88a73df0 R08: 0000000001bbbbbb R09: 0000000001bbbbbb
R10: 0000000001bbbbbb R11: 0000000000000246 R12: 00007ffe88a73e00
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000