syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-...!: (1 GPs behind) idle=05a/1/0x4000000000000002 softirq=13830/13831 fqs=40 
	(t=10500 jiffies g=6873 q=105)
rcu: rcu_preempt kthread starved for 10418 jiffies! g6873 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: RCU grace-period kthread stack dump:
rcu_preempt     R  running task    28984    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
NMI backtrace for cpu 1
CPU: 1 PID: 8583 Comm: syz-executor.5 Not tainted 5.5.0-rc5-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+0x1fb/0x318 lib/dump_stack.c:118
 nmi_cpu_backtrace+0xaf/0x1a0 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x174/0x290 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x15a/0x220 kernel/rcu/tree_stall.h:254
 print_cpu_stall kernel/rcu/tree_stall.h:455 [inline]
 check_cpu_stall kernel/rcu/tree_stall.h:529 [inline]
 rcu_pending kernel/rcu/tree.c:2827 [inline]
 rcu_sched_clock_irq+0xe25/0x1ad0 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:__read_once_size include/linux/compiler.h:199 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:155 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x1c/0x50 kernel/kcov.c:187
Code: ed 07 48 89 de e8 84 f4 3b 00 5b 5d c3 cc 48 8b 04 24 65 48 8b 0c 25 c0 1d 02 00 65 8b 15 38 5f 8b 7e f7 c2 00 01 1f 00 75 2c <8b> 91 80 13 00 00 83 fa 02 75 21 48 8b 91 88 13 00 00 48 8b 32 48
RSP: 0018:ffffc900024c72b0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffffffff81489244 RBX: ffffea00025a7f80 RCX: ffff88809f822240
RDX: 0000000000000001 RSI: 00000000fffffffc RDI: ffffea00025a7f80
RBP: ffffc900024c72f0 R08: 000000000003a728 R09: ffffed1015076aa1
R10: ffffed1015076aa1 R11: 0000000000000000 R12: ffff88809de973a0
R13: dffffc0000000000 R14: 1ffff11013bd2e74 R15: ffff8880a83b54f8
 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_common kernel/sched/core.c:4236 [inline]
 preempt_schedule+0xdb/0x120 kernel/sched/core.c:4261
 ___preempt_schedule+0x16/0x18 arch/x86/entry/thunk_64.S:50
 try_to_wake_up+0xe78/0x1050 kernel/sched/core.c:2650
 wake_up_process kernel/sched/core.c:2668 [inline]
 wake_up_q+0x8c/0xe0 kernel/sched/core.c:496
 __mutex_unlock_slowpath+0x586/0x5b0 kernel/locking/mutex.c:1280
 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:740
 __rtnl_unlock+0x2c/0xa0 net/core/rtnetlink.c:98
 netdev_run_todo+0xe5/0xe10 net/core/dev.c:9546
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:112
 nsim_create+0x224/0x230 drivers/net/netdevsim/netdev.c:312
 __nsim_dev_port_add+0x289/0x4d0 drivers/net/netdevsim/dev.c:648
 nsim_dev_port_add_all drivers/net/netdevsim/dev.c:697 [inline]
 nsim_dev_probe+0xb55/0xef0 drivers/net/netdevsim/dev.c:818
 nsim_bus_probe+0x15/0x20 drivers/net/netdevsim/bus.c:242
 really_probe+0x71c/0xf40 drivers/base/dd.c:548
 driver_probe_device+0xfc/0x260 drivers/base/dd.c:721
 __device_attach_driver+0x336/0x3f0 drivers/base/dd.c:828
 bus_for_each_drv+0x12b/0x180 drivers/base/bus.c:430
 __device_attach+0x1ea/0x390 drivers/base/dd.c:894
 device_initial_probe+0x1a/0x20 drivers/base/dd.c:941
 bus_probe_device+0xb9/0x1f0 drivers/base/bus.c:490
 device_add+0x1710/0x1ad0 drivers/base/core.c:2487
 device_register+0x1d/0x20 drivers/base/core.c:2560
 nsim_bus_dev_new drivers/net/netdevsim/bus.c:288 [inline]
 new_device_store+0x286/0x510 drivers/net/netdevsim/bus.c:182
 bus_attr_store+0x78/0x90 drivers/base/bus.c:121
 sysfs_kf_write+0x281/0x2f0 fs/sysfs/file.c:138
 kernfs_fop_write+0x3fd/0x500 fs/kernfs/file.c:315
 __vfs_write+0xb8/0x740 fs/read_write.c:494
 vfs_write+0x275/0x590 fs/read_write.c:558
 ksys_write+0x117/0x220 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:620
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x414a00
Code: b0 89 c8 f7 d8 eb ed b8 6e 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 83 3d 6d 3a 66 00 00 75 14 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 c4 1b 00 00 c3 48 83 ec 08 e8 ca fc ff ff
RSP: 002b:00007ffc8681e308 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000414a00
RDX: 0000000000000003 RSI: 00007ffc8681e330 RDI: 0000000000000004
RBP: 00007ffc8681e330 R08: 0000000000000000 R09: 0000000000000003
R10: 0000000000000075 R11: 0000000000000246 R12: 00000000004c05e5
R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000