INFO: task syz-executor6:14496 blocked for more than 120 seconds.
      Not tainted 4.9.76-gf0f6293 #12
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor6   D28800 14496   5098 0x00000004
 ffff8801c7a5c800 ffff8801caf95f80 ffff8801d58d2a00 ffff8801cacb0000
 ffff8801db221b98 ffff8801cad9fab0 ffffffff8389f9fb 0000000000000002
 0000000041b58ab3 00ffffff8418999c ffff8801db222468 ffff8801db222490
Call Trace:
 [<ffffffff838a0f9f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3550
 [<ffffffff8128d4b7>] exp_funnel_lock kernel/rcu/tree_exp.h:279 [inline]
 [<ffffffff8128d4b7>] _synchronize_rcu_expedited+0x3c7/0x800 kernel/rcu/tree_exp.h:569
 [<ffffffff81290432>] synchronize_rcu_expedited+0x22/0x30 kernel/rcu/tree_exp.h:687
 [<ffffffff82f2d7c0>] synchronize_net+0x40/0x50 net/core/dev.c:7808
 [<ffffffff8355064d>] packet_release+0x7bd/0x990 net/packet/af_packet.c:3032
 [<ffffffff82ed289d>] sock_release+0x8d/0x1e0 net/socket.c:599
 [<ffffffff82ed8b33>] SYSC_socketpair net/socket.c:1369 [inline]
 [<ffffffff82ed8b33>] SyS_socketpair+0x423/0x510 net/socket.c:1273
 [<ffffffff838b0aa8>] entry_SYSCALL_64_fastpath+0x23/0xe2

Showing all locks held in the system:
2 locks held by khungtaskd/514:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81371d35>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81371d35>] watchdog+0x125/0xa70 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81236eb0>] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336
2 locks held by getty/3300:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838aec72>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+.+.}, at: [<ffffffff82008494>] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.76-gf0f6293 #12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d8f37d00 ffffffff81d93149 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810ba750 ffff8801d8f37d38
 ffffffff81d9e26d 0000000000000001 0000000000000000 ffff8801cb636418
Call Trace:
 [<ffffffff81d93149>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d93149>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81d9e26d>] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99
 [<ffffffff81d9e3a7>] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60
 [<ffffffff810ba844>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81372300>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81372300>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81372300>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81372300>] watchdog+0x6f0/0xa70 kernel/hung_task.c:239
 [<ffffffff811996ad>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838b0db6>] ret_from_fork+0x46/0x60 arch/x86/entry/entry_64.S:460
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838af6e6