INFO: task syz.7.912:9727 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.7.912       state:D stack:25128 pid:9727  tgid:9726  ppid:8102   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x1798/0x4cc0
 schedule+0x165/0x360
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7e6/0x1350
 sync_bdevs+0x1ac/0x340
 ksys_sync+0xb9/0x150
 __ia32_sys_sync+0xe/0x20
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9514b8ec29
RSP: 002b:00007f9515a0c038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 00007f9514dd5fa0 RCX: 00007f9514b8ec29
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f9514dd5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9514dd6038 R14: 00007f9514dd5fa0 R15: 00007fffeedd66d8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8e33d320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
4 locks held by kworker/0:2/793:
 #0: ffff88801bf96948 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0
 #1: ffffc90004fd7ba0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0
 #2: ffff88810a05f198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20
 #3: ffff88811ac06198 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400
2 locks held by getty/5672:
 #0: ffff8880210040a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900029062f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400
4 locks held by udevd/5856:
 #0: ffff8881255650a0 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb7/0xe20
 #1: ffff88802646a888 (&of->mutex#2){+.+.}-{4:4}, at: kernfs_seq_start+0x5c/0x420
 #2: ffff88810b4c4a58 (kn->active#30){++++}-{0:0}, at: kernfs_seq_start+0xb2/0x420
 #3: ffff88811ac06198 (&dev->mutex){....}-{4:4}, at: manufacturer_show+0x26/0xa0
1 lock held by udevd/6027:
 #0: ffff888108453358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xe0/0xd30
1 lock held by syz.7.912/9727:
 #0: ffff888108453358 (&disk->open_mutex){+.+.}-{4:4}, at: sync_bdevs+0x1ac/0x340

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 34 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 nmi_cpu_backtrace+0x39e/0x3d0
 nmi_trigger_cpumask_backtrace+0x17a/0x300
 watchdog+0xf60/0xfa0
 kthread+0x711/0x8a0
 ret_from_fork+0x4bc/0x870
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 12725 Comm: syz.2.1634 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:check_preemption_disabled+0x63/0x120
Code: 08 0f 85 cc 00 00 00 48 83 c4 10 5b 41 5e 41 5f 5d c3 cc cc cc cc cc 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <74> c8 65 4c 8b 3c 25 08 40 c2 92 41 f6 47 2f 04 74 0a 41 83 bf 58
RSP: 0018:ffffc900283ff9a8 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffffc900283ffa48 RCX: 0000000080000000
RDX: 0000000000000000 RSI: ffffffff8bac1ec0 RDI: ffffffff8c03da60
RBP: 0000000000000000 R08: ffffffff8fc35777 R09: 1ffffffff1f86aee
R10: dffffc0000000000 R11: fffffbfff1f86aef R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000002 R15: dffffc0000000000
FS:  00007f5a72b366c0(0000) GS:ffff8881a39fc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000b67000 CR3: 00000001159f2000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 rcu_irq_exit_check_preempt+0x63/0x210
 raw_irqentry_exit_cond_resched+0x17/0x50
 irqentry_exit+0x6f/0x90
 exc_page_fault+0xab/0x100
 asm_exc_page_fault+0x26/0x30
RIP: 0010:rep_movs_alternative+0x54/0x90
Code: 00 00 00 0f 1f 00 48 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08 73 e8 eb c5 eb 05 e9 8f 2e 04 00 48 8b 06 <48> 89 07 48 8d 47 08 48 83 e0 f8 48 29 f8 48 01 c7 48 01 c6 48 29
RSP: 0018:ffffc900283ffaf8 EFLAGS: 00010246
RAX: 230674b2a84a7f75 RBX: ffffc900283ffd20 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffc900283ffd20 RDI: 0000200000b67000
RBP: ffffc900283ffc70 R08: ffffc900283ffd5f R09: 1ffff9200507ffab
R10: dffffc0000000000 R11: fffff5200507ffac R12: 1ffff9200507ffc5
R13: 0000200000b67000 R14: ffffc900283ffe38 R15: 0000000000000040
 _copy_to_iter+0x24f/0x1790
 get_random_bytes_user+0x1a0/0x380
 __x64_sys_getrandom+0x16d/0x260
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5a71d8ec29
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f5a72b36038 EFLAGS: 00000246 ORIG_RAX: 000000000000013e
RAX: ffffffffffffffda RBX: 00007f5a71fd6090 RCX: 00007f5a71d8ec29
RDX: 0000000000000000 RSI: 00000000ffffff9a RDI: 0000200000000240
RBP: 00007f5a71e11e41 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5a71fd6128 R14: 00007f5a71fd6090 R15: 00007fff2f083c98
 </TASK>
