pktgen: kernel_thread() failed for cpu 0
pktgen: Cannot create thread for cpu 0 (-4)
pktgen: kernel_thread() failed for cpu 1
pktgen: Cannot create thread for cpu 1 (-4)
pktgen: Initialization failed for all threads
INFO: task syz-executor5:21667 blocked for more than 120 seconds.
      Not tainted 4.9.106-g8b94b87 #46
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor5   D29088 21667   3878 0x00000004
 ffff88019283c800 0000000000000000 ffff8801d5712a00 ffffffff84629800
 ffff8801db221c18 ffff8801d30c79f0 ffffffff839e8c0d 0000000000000002
 0000000041b58ab3 ffffffff843b9ceb 00ffffff81221500 ffff8801db2224e8
Call Trace:
 [<ffffffff839ea20f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff81e41904>] blk_mq_freeze_queue_wait+0x114/0x230 block/blk-mq.c:75
 [<ffffffff81e4abfd>] blk_freeze_queue block/blk-mq.c:92 [inline]
 [<ffffffff81e4abfd>] blk_mq_freeze_queue+0x1d/0x20 block/blk-mq.c:101
 [<ffffffff825cb262>] loop_switch drivers/block/loop.c:599 [inline]
 [<ffffffff825cb262>] loop_change_fd drivers/block/loop.c:685 [inline]
 [<ffffffff825cb262>] lo_ioctl+0x722/0x1aa0 drivers/block/loop.c:1350
 [<ffffffff81e57e06>] __blkdev_driver_ioctl block/ioctl.c:294 [inline]
 [<ffffffff81e57e06>] blkdev_ioctl+0x7b6/0x1a70 block/ioctl.c:590
 [<ffffffff81632f9e>] block_ioctl+0xde/0x120 fs/block_dev.c:1688
 [<ffffffff815b2fac>] vfs_ioctl fs/ioctl.c:43 [inline]
 [<ffffffff815b2fac>] file_ioctl fs/ioctl.c:493 [inline]
 [<ffffffff815b2fac>] do_vfs_ioctl+0x1ac/0x11a0 fs/ioctl.c:677
 [<ffffffff815b402f>] SYSC_ioctl fs/ioctl.c:694 [inline]
 [<ffffffff815b402f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:685
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Showing all locks held in the system:
2 locks held by khungtaskd/519:
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b6c>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff81366b6c>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81426150>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
1 lock held by rsyslogd/3671:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d844c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3773:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff839f7cb2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff821200c2>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2133
1 lock held by syz-executor5/21667:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cabcb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344
1 lock held by blkid/21686:
 #0:  (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<ffffffff825cabcb>] lo_ioctl+0x8b/0x1aa0 drivers/block/loop.c:1344

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

NMI backtrace for cpu 1
CPU: 1 PID: 519 Comm: khungtaskd Not tainted 4.9.106-g8b94b87 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d85cfd08 ffffffff81eb4209 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b96a0 ffff8801d85cfd40
 ffffffff81ebf507 0000000000000001 0000000000000000 0000000000000003
Call Trace:
 [<ffffffff81eb4209>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb4209>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81ebf507>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81ebf49a>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b97a4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81367104>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81367104>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81367104>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81367104>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119d04d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839f9cdc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 3669 Comm: rs:main Q:Reg Not tainted 4.9.106-g8b94b87 #46
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801c56a9800 task.stack: ffff8801c5528000
RIP: 0010:[<ffffffff8123761a>] 
c [<ffffffff8123761a>] lookup_chain_cache kernel/locking/lockdep.c:2139 [inline]
RIP: 0010:[<ffffffff8123761a>] 
c [<ffffffff8123761a>] validate_chain kernel/locking/lockdep.c:2236 [inline]
RIP: 0010:[<ffffffff8123761a>] 
c [<ffffffff8123761a>] __lock_acquire+0xf7a/0x4070 kernel/locking/lockdep.c:3345
RSP: 0018:ffff8801c552f2b0  EFLAGS: 00000046
RAX: dffffc0000000000 RBX: ffff8801c56aa1b8 RCX: 00000000d59b8dd1
RDX: 1ffffffff09f4927 RSI: ffff8801c56aa1b8 RDI: ffffffff84fa4938
RBP: ffff8801c552f458 R08: ffff8801c56aa1d8 R09: 0000000000000000
R10: ffff8801c56a9800 R11: 1ffff10038ad5436 R12: ffffffff84fa4928
R13: 0000000000000000 R14: 0000000061e93d54 R15: 80043437ee7959bc
FS:  00007f7af5a10700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fabd4632000 CR3: 00000001c6a84000 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 0000000041b58ab3
c ffffffff843c21d0
c ffffffff812366a0
c ffffffff8554ded0
c
 0000000041b58ab3
c ffff8801c56a9800
c ffffed0038ad5418
c ffff8801c56aa0c8
c
 ffffffff846def20
c 0000000000000004
c ffffffff855e3d30
c ffffffff81230712
c
Call Trace:
 [<ffffffff8123b180>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff839f8ea6>] __raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
 [<ffffffff839f8ea6>] _raw_spin_lock+0x36/0x50 kernel/locking/spinlock.c:151
 [<ffffffff818264e3>] spin_lock include/linux/spinlock.h:302 [inline]
 [<ffffffff818264e3>] ext4_discard_preallocations+0x1e3/0xc90 fs/ext4/mballoc.c:3988
 [<ffffffff81754c16>] ext4_truncate+0x9d6/0x12c0 fs/ext4/inode.c:4256
 [<ffffffff81756deb>] ext4_truncate_failed_write fs/ext4/truncate.h:15 [inline]
 [<ffffffff81756deb>] ext4_da_write_begin+0x4eb/0x1020 fs/ext4/inode.c:3015
 [<ffffffff81436121>] generic_perform_write+0x301/0x510 mm/filemap.c:2740
 [<ffffffff8143dbb2>] __generic_file_write_iter+0x352/0x540 mm/filemap.c:2865
 [<ffffffff8172d343>] ext4_file_write_iter+0x463/0xd90 fs/ext4/file.c:165
 [<ffffffff8156ef70>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff8156ef70>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff81572d67>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff81576b99>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff81576b99>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Code: 
ce4 
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c<0f> 
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c