INFO: task syz-executor4:6384 blocked for more than 120 seconds.
      Not tainted 4.4.115-gaa856bd #6
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor4   D ffff8800bbb2f768 28136  6384   3794 0x00000004
 ffff8800bbb2f768 0000000000000000 0000000000000000 0000000000000000
 0000000000000001 ffff8800bbb2f700 ffff8801db21fdb8 ffff8801db21fde0
 ffff8801db21f4d8 ffff8801c4e74800 ffff8800aeb88000 0000000000000000
Call Trace:
 [<ffffffff837662da>] schedule+0x7a/0x1b0 kernel/sched/core.c:3353
 [<ffffffff83766ad3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3386
 [<ffffffff8376b096>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff8376b096>] mutex_lock_nested+0x306/0x850 kernel/locking/mutex.c:621
 [<ffffffff82d427ff>] odev_open+0x5f/0x90 sound/core/seq/oss/seq_oss.c:136
 [<ffffffff82ca1781>] soundcore_open+0x321/0x630 sound/sound_core.c:639
 [<ffffffff81529dab>] chrdev_open+0x22b/0x4c0 fs/char_dev.c:388
 [<ffffffff81517f7b>] do_dentry_open+0x59b/0xba0 fs/open.c:749
 [<ffffffff8151b840>] vfs_open+0x110/0x210 fs/open.c:862
 [<ffffffff8154caa3>] do_last fs/namei.c:3217 [inline]
 [<ffffffff8154caa3>] path_openat+0x923/0x3940 fs/namei.c:3353
 [<ffffffff81552747>] do_filp_open+0x197/0x290 fs/namei.c:3388
 [<ffffffff8151c219>] do_sys_open+0x369/0x660 fs/open.c:1038
 [<ffffffff8151c580>] SYSC_openat fs/open.c:1065 [inline]
 [<ffffffff8151c580>] SyS_openat+0x30/0x40 fs/open.c:1059
 [<ffffffff8377441f>] entry_SYSCALL_64_fastpath+0x1c/0x98
INFO: lockdep is turned off.
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 485 Comm: khungtaskd Not tainted 4.4.115-gaa856bd #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8800bb93b000 task.stack: ffff8800bb020000
RIP: 0010:[<ffffffff810c3ec7>]  [<ffffffff810c3ec7>] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline]
RIP: 0010:[<ffffffff810c3ec7>]  [<ffffffff810c3ec7>] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline]
RIP: 0010:[<ffffffff810c3ec7>]  [<ffffffff810c3ec7>] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline]
RIP: 0010:[<ffffffff810c3ec7>]  [<ffffffff810c3ec7>] flat_send_IPI_mask+0xf7/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69
RSP: 0018:ffff8800bb027cb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: ffffffff8126a292
RDX: 0000000000000c00 RSI: 0000000000000002 RDI: ffffffffff5fb300
RBP: ffff8800bb027ce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: fffffbfff0ad7e2c R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f3a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c422d3d000 CR3: 00000001ceb6c000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f3a0 ffffffff847ef7c0 fffffbfff08fd9ac dffffc0000000000
 ffff8801db31bca0 ffff8800bb027d00 ffffffff810b99fb ffffffff839f61c0
 0000000000000003 ffff8800bb027d60 ffffffff81d0ed14 0000000000000001
Call Trace:
 [<ffffffff810b99fb>] nmi_raise_cpu_backtrace+0x5b/0x70 arch/x86/kernel/apic/hw_nmi.c:33
 [<ffffffff81d0ed14>] nmi_trigger_all_cpu_backtrace+0x4a4/0x550 lib/nmi_backtrace.c:85
 [<ffffffff810b9a94>] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 [<ffffffff81368cca>] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline]
 [<ffffffff81368cca>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81368cca>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81368cca>] watchdog+0x6fa/0xae0 kernel/hung_task.c:238
 [<ffffffff811907e8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff83774845>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:506
Code: b3 5f ff f6 c4 10 75 e1 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 74 1a e8 0b 2f 17 00 4c 89 e7 57 9d 0f 1f 
NMI backtrace for cpu 1
CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.115-gaa856bd #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffff8801d9b49800 task.stack: ffff8801d9b58000
RIP: 0010:[<ffffffff81285e40>]  [<ffffffff81285e40>] debug_lockdep_rcu_enabled+0x0/0x90 kernel/rcu/update.c:243
RSP: 0018:ffff8801d9b5fca8  EFLAGS: 00000002
RAX: 0000000000000000 RBX: 1ffffffff070887c RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801d9b4a0cc
RBP: ffff8801d9b5fd60 R08: 0000000000000000 R09: 0000000000000001
R10: 0000000000000000 R11: 1ffff1003b36bf7a R12: ffffffff857036c8
R13: ffff8801db319cd0 R14: ffffffff847ebc38 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe9c532f000 CR3: 00000000b0094000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8123e212 ffff8801d9b49800 0000000000000000 0000000000000000
 0000000000000002 0000000000000001 ffff8801d9b5fd60 0000000000000046
 0000000000000000 ffffffff812d77c3 0000000000000000 0000000000000000
Call Trace:
 [<ffffffff812c017b>] seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline]
 [<ffffffff812c017b>] read_seqcount_begin include/linux/seqlock.h:163 [inline]
 [<ffffffff812c017b>] ktime_get+0x8b/0x1d0 kernel/time/timekeeping.c:756
 [<ffffffff812d77c3>] tick_nohz_idle_exit+0x153/0x3d0 kernel/time/tick-sched.c:940
 [<ffffffff81221815>] cpu_idle_loop kernel/sched/idle.c:267 [inline]
 [<ffffffff81221815>] cpu_startup_entry+0x2a5/0x8f0 kernel/sched/idle.c:301
 [<ffffffff810adcc4>] start_secondary+0x304/0x3e0 arch/x86/kernel/smpboot.c:242
Code: 7c 04 84 d2 75 10 8b 93 cc 08 00 00 31 c0 5b 5d 85 d2 0f 94 c0 c3 e8 f0 89 27 00 eb e9 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 <48> c7 c7 e4 bc 7e 84 55 48 b8 00 00 00 00 00 fc ff df 48 89 fa