INFO: task syz-executor.0:20696 blocked for more than 140 seconds.
      Not tainted 4.9.180+ #4
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.0  D28744 20696   2079 0x80000000
 0000000000000083 ffff8801cb03df00 0000000000000000 ffff8801db621000
 ffff8801cf61c740 ffff8801db621018 ffff8801c8f1fba0 ffffffff8280924e
 0000000041b58ab3 ffff8801cb03df00 00ff8801c8f1faf0 ffff8801db6218f0
Call Trace:
 [<00000000e3c79803>] schedule+0x92/0x1c0 kernel/sched/core.c:3546
 [<00000000d9611372>] rwsem_down_read_failed+0x258/0x3e0 kernel/locking/rwsem-xadd.c:283
 [<00000000adb863e2>] call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
 [<000000008078ba03>] __down_read arch/x86/include/asm/rwsem.h:65 [inline]
 [<000000008078ba03>] down_read+0x52/0xb0 kernel/locking/rwsem.c:24
 [<0000000057279c13>] exit_mm kernel/exit.c:480 [inline]
 [<0000000057279c13>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828
 [<000000003395324f>] do_group_exit+0x111/0x300 kernel/exit.c:945
 [<000000007008cba0>] SYSC_exit_group kernel/exit.c:956 [inline]
 [<000000007008cba0>] SyS_exit_group+0x1d/0x20 kernel/exit.c:954
 [<00000000700f599f>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<0000000041edea08>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/24:
 #0:  (rcu_read_lock){......}, at: [<00000000662547c2>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline]
 #0:  (rcu_read_lock){......}, at: [<00000000662547c2>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263
 #1:  (tasklist_lock){.+.+..}, at: [<000000002931da6b>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336
2 locks held by getty/2026:
 #0:  (&tty->ldisc_sem){++++++}, at: [<00000000d8ecd42a>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<00000000d906e554>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156
1 lock held by syz-executor.0/20696:
 #0:  (&mm->mmap_sem){++++++}, at: [<0000000057279c13>] exit_mm kernel/exit.c:480 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<0000000057279c13>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828
1 lock held by syz-executor.0/20699:
 #0:  (&mm->mmap_sem){++++++}, at: [<0000000057279c13>] exit_mm kernel/exit.c:480 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<0000000057279c13>] do_exit+0x3b7/0x2aa0 kernel/exit.c:828

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

NMI backtrace for cpu 0
CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.180+ #4
 ffff8801d98d7cc8 ffffffff81b577f1 0000000000000000 0000000000000000
 0000000000000000 ffffffff81099901 dffffc0000000000 ffff8801d98d7d00
 ffffffff81b62a8c 0000000000000000 0000000000000000 0000000000000000
Call Trace:
 [<00000000cb845d0a>] __dump_stack lib/dump_stack.c:15 [inline]
 [<00000000cb845d0a>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<00000000dfcadf79>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99
 [<000000001e6d11b6>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60
 [<00000000703c9bac>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<00000000d49213e8>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<00000000d49213e8>] check_hung_task kernel/hung_task.c:126 [inline]
 [<00000000d49213e8>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline]
 [<00000000d49213e8>] watchdog+0x670/0xaf0 kernel/hung_task.c:263
 [<0000000099017571>] kthread+0x278/0x310 kernel/kthread.c:211
 [<00000000dfe4919e>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 20710 Comm: syz-executor.0 Not tainted 4.9.180+ #4
task: 0000000068ad7c69 task.stack: 0000000096cc1746
RIP: 0010:[<ffffffff811697c1>] 
c [<000000005bafc41f>] preempt_latency_start kernel/sched/core.c:3219 [inline]
RIP: 0010:[<ffffffff811697c1>] 
c [<000000005bafc41f>] preempt_count_add+0xd1/0x1c0 kernel/sched/core.c:3242
RSP: 0018:ffff8801c7577b18  EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffffffff8280d133 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 000000000000026c RDI: ffff8801ca66a970
RBP: ffff8801c7577b28 R08: 0000000000000000 R09: ffff8801ca66a090
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801ca6697c0
R13: ffff8801cff86060 R14: ffffffff813dfd89 R15: ffff8801cff86060
FS:  00007f91ba633700(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000001968a00 CR3: 00000001c8512000 CR4: 00000000001606b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 dffffc0000000000
c 0000000000000000
c ffff8801c7577c28
c ffffffff8280d133
c
 0000000000000246
c 1ffff10038eaef70
c ffffffff8120b485
c 0000000000000003
c
 ffff8801cff86060
c ffff8801c7577bb0
c 1ffff10038eaef72
c ffff8801c7577c18
c
Call Trace:
 [<000000005c04e8fa>] __mutex_lock_common kernel/locking/mutex.c:520 [inline]
 [<000000005c04e8fa>] mutex_lock_nested+0xa3/0x920 kernel/locking/mutex.c:621
 [<000000007725a5cf>] perf_mmap+0x4d9/0x1580 kernel/events/core.c:5278
 [<00000000421fd6e9>] mmap_region+0x7e7/0xfa0 mm/mmap.c:1726
 [<000000006b35aa62>] do_mmap+0x539/0xbc0 mm/mmap.c:1505
 [<00000000ee3441b9>] do_mmap_pgoff include/linux/mm.h:2043 [inline]
 [<00000000ee3441b9>] vm_mmap_pgoff+0x179/0x1c0 mm/util.c:329
 [<00000000fb2a40cf>] SYSC_mmap_pgoff mm/mmap.c:1555 [inline]
 [<00000000fb2a40cf>] SyS_mmap_pgoff+0xfa/0x1b0 mm/mmap.c:1513
 [<000000005484fc6b>] SYSC_mmap arch/x86/kernel/sys_x86_64.c:96 [inline]
 [<000000005484fc6b>] SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:87
 [<00000000700f599f>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 [<0000000041edea08>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
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c