syzbot

INFO: task syzkaller589832:3782 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.
syzkaller589832 D ffff8800ba48f7a8 27240  3782   3780 0x00000000
 ffff8800ba48f7a8 0000000000000000 0000000000000000 0000000000000000
 0000000000000001 ffff8800ba48f700 ffff8801db31fdb8 ffff8801db31fde0
 ffff8801db31f4d8 ffff8801d9b49800 ffff8801d8f06000 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
 [<ffffffff82d2ad8d>] snd_seq_do_ioctl+0x15d/0x1b0 sound/core/seq/seq_clientmgr.c:2214
 [<ffffffff82d2aeb7>] snd_seq_kernel_client_ctl+0xd7/0x150 sound/core/seq/seq_clientmgr.c:2432
 [<ffffffff82d54150>] snd_seq_oss_control sound/core/seq/oss/seq_oss_device.h:157 [inline]
 [<ffffffff82d54150>] snd_seq_oss_writeq_clear+0xe0/0x140 sound/core/seq/oss/seq_oss_writeq.c:84
 [<ffffffff82d541cf>] snd_seq_oss_writeq_delete+0x1f/0x30 sound/core/seq/oss/seq_oss_writeq.c:68
 [<ffffffff82d42d71>] free_devinfo+0x61/0xb0 sound/core/seq/oss/seq_oss_init.c:406
 [<ffffffff82d3d015>] port_delete+0xd5/0x110 sound/core/seq/seq_ports.c:273
 [<ffffffff82d3d913>] snd_seq_delete_port+0x1c3/0x200 sound/core/seq/seq_ports.c:303
 [<ffffffff82d29142>] snd_seq_ioctl_delete_port+0xf2/0x1d0 sound/core/seq/seq_clientmgr.c:1326
 [<ffffffff82d2adb2>] snd_seq_do_ioctl+0x182/0x1b0 sound/core/seq/seq_clientmgr.c:2215
 [<ffffffff82d2aeb7>] snd_seq_kernel_client_ctl+0xd7/0x150 sound/core/seq/seq_clientmgr.c:2432
 [<ffffffff82d3bd5f>] snd_seq_event_port_detach+0xaf/0x100 sound/core/seq/seq_ports.c:706
 [<ffffffff82d42e33>] delete_port+0x73/0xb0 sound/core/seq/oss/seq_oss_init.c:354
 [<ffffffff82d43fe4>] snd_seq_oss_release+0xe4/0x130 sound/core/seq/oss/seq_oss_init.c:433
 [<ffffffff82d42782>] odev_release+0x52/0x70 sound/core/seq/oss/seq_oss.c:152
 [<ffffffff815236a3>] __fput+0x233/0x6d0 fs/file_table.c:208
 [<ffffffff81523bc5>] ____fput+0x15/0x20 fs/file_table.c:244
 [<ffffffff8118b9e4>] task_work_run+0x104/0x180 kernel/task_work.c:115
 [<ffffffff8100361d>] tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 [<ffffffff8100361d>] exit_to_usermode_loop+0x13d/0x160 arch/x86/entry/common.c:251
 [<ffffffff81006535>] prepare_exit_to_usermode arch/x86/entry/common.c:282 [inline]
 [<ffffffff81006535>] syscall_return_slowpath+0x1b5/0x1f0 arch/x86/entry/common.c:347
 [<ffffffff837745a9>] int_ret_from_sys_call+0x25/0xa3
INFO: lockdep is turned off.
Sending NMI to all CPUs:
NMI backtrace for cpu 0
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.115-gaa856bd #6
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
task: ffffffff84217840 task.stack: ffffffff84200000
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] __read_once_size include/linux/compiler.h:218 [inline]
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] atomic_read arch/x86/include/asm/atomic.h:27 [inline]
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] static_key_count include/linux/jump_label.h:172 [inline]
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] static_key_false include/linux/jump_label.h:182 [inline]
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] sched_clock_stable kernel/sched/clock.c:85 [inline]
RIP: 0010:[<ffffffff811d40a6>]  [<ffffffff811d40a6>] sched_clock_tick+0x6/0x120 kernel/sched/clock.c:322
RSP: 0018:ffffffff84207dc0  EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff8801db219c40 RCX: ffffffff812d51d6
RDX: 0000000000000000 RSI: ffff8801db219c40 RDI: ffffffff847ebd14
RBP: ffffffff84207dc8 R08: ffff88021fffd018 R09: 000000000000000a
R10: ffffed0043fffa01 R11: 0000000000000000 R12: 0000008bf6e3bc5d
R13: ffff8801db219cd0 R14: 0000008bf6e3bc5d R15: ffffffff84208000
FS:  0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4f4e271000 CR3: 00000001cc32e000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff811d4202 ffffffff84207de8 ffffffff812d573b ffff8801db219c40
 ffff8801db219cb4 ffffffff84207e20 ffffffff812d793f ffffffff84207e10
 dffffc0000000000 ffffffff847dd8c8 fffffbfff070887c ffffffff847ebc38
Call Trace:
 [<ffffffff812d573b>] tick_nohz_stop_idle+0x5b/0x70 kernel/time/tick-sched.c:463
 [<ffffffff812d793f>] tick_nohz_idle_exit+0x2cf/0x3d0 kernel/time/tick-sched.c:943
 [<ffffffff81221815>] cpu_idle_loop kernel/sched/idle.c:267 [inline]
 [<ffffffff81221815>] cpu_startup_entry+0x2a5/0x8f0 kernel/sched/idle.c:301
 [<ffffffff83761369>] rest_init+0x189/0x190 init/main.c:410
 [<ffffffff84821811>] start_kernel+0x6b9/0x6ee init/main.c:682
 [<ffffffff84820312>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84820454>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:185
Code: c0 7f 0e 65 8b 3d 93 20 e4 7e e8 c6 fd ff ff 5d c3 e8 af 20 e5 ff 5d c3 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 8b 05 da e1 84 03 <85> c0 0f 8f b9 00 00 00 8b 05 d8 7b 61 03 85 c0 0f 84 ab 00 00 
NMI backtrace for cpu 1
CPU: 1 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: ffff8800bac90000 task.stack: ffff8800bace0000
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:ffff8800bace7cb8  EFLAGS: 00000046
RAX: 0000000003000000 RBX: 0000000000000c00 RCX: ffffffff8126a292
RDX: 0000000000000c00 RSI: 0000000000000002 RDI: ffffffffff5fb300
RBP: ffff8800bace7ce0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: fffffbfff0ad7e2c R12: 0000000000000246
R13: 0000000000000003 R14: ffffffff8426f3a0 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000020d2000 CR3: 00000001cc32e000 CR4: 0000000000160670
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
 ffffffff8426f3a0 ffffffff847ef7c0 fffffbfff08fd9ac dffffc0000000000
 ffff8801db31bca0 ffff8800bace7d00 ffffffff810b99fb ffffffff839f61c0
 0000000000000003 ffff8800bace7d60 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