INFO: task syz-executor.4:29078 blocked for more than 143 seconds.
      Not tainted 5.1.0-rc4-next-20190411 #23
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.4  D27144 29078   9218 0x80000002
Call Trace:
 context_switch kernel/sched/core.c:2877 [inline]
 __schedule+0x817/0x1cc0 kernel/sched/core.c:3518
 schedule+0x92/0x180 kernel/sched/core.c:3562
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3620
 __mutex_lock_common kernel/locking/mutex.c:1002 [inline]
 __mutex_lock+0x726/0x1310 kernel/locking/mutex.c:1072
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087
 snd_seq_kernel_client_ctl+0xe5/0x170 sound/core/seq/seq_clientmgr.c:2345
 snd_seq_oss_control sound/core/seq/oss/seq_oss_device.h:157 [inline]
 snd_seq_oss_writeq_clear+0xe0/0x140 sound/core/seq/oss/seq_oss_writeq.c:85
 snd_seq_oss_writeq_delete+0x20/0x40 sound/core/seq/oss/seq_oss_writeq.c:69
 free_devinfo+0x66/0xc0 sound/core/seq/oss/seq_oss_init.c:406
 port_delete+0xe8/0x1c0 sound/core/seq/seq_ports.c:272
 snd_seq_delete_port+0x266/0x330 sound/core/seq/seq_ports.c:301
 snd_seq_ioctl_delete_port+0xba/0x190 sound/core/seq/seq_clientmgr.c:1321
 snd_seq_kernel_client_ctl+0x112/0x170 sound/core/seq/seq_clientmgr.c:2346
 snd_seq_event_port_detach+0xba/0x100 sound/core/seq/seq_ports.c:705
 delete_port+0x87/0xd0 sound/core/seq/oss/seq_oss_init.c:354
 snd_seq_oss_release+0xf5/0x150 sound/core/seq/oss/seq_oss_init.c:433
 odev_release+0x54/0x80 sound/core/seq/oss/seq_oss.c:153
 __fput+0x2e5/0x8d0 fs/file_table.c:278
 ____fput+0x16/0x20 fs/file_table.c:309
 task_work_run+0x14a/0x1c0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x90a/0x2fa0 kernel/exit.c:876
 do_group_exit+0x135/0x370 kernel/exit.c:980
 get_signal+0x399/0x1d50 kernel/signal.c:2578
 do_signal+0x87/0x1940 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x244/0x2c0 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x52d/0x610 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4582f9
Code: 24 20 48 8b 42 08 48 89 44 24 18 48 63 4a 10 48 89 4c 24 10 e8 78 3f fd ff 48 8d 05 9a 70 48 00 48 89 04 24 48 c7 44 24 08 11 <00> 00 00 e8 ff 48 fd ff 48 8b 44 24 18 48 89 04 24 e8 b1 48 fd ff
RSP: 002b:00007f8fb7564cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000073bf08 RCX: 00000000004582f9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000073bf08
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000073bf0c
R13: 00007ffcdf0052af R14: 00007f8fb75659c0 R15: 000000000073bf0c
INFO: lockdep is turned off.
NMI backtrace for cpu 1
CPU: 1 PID: 1045 Comm: khungtaskd Not tainted 5.1.0-rc4-next-20190411 #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1be/0x236 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:204 [inline]
 watchdog+0x9b7/0xec0 kernel/hung_task.c:288
 kthread+0x357/0x430 kernel/kthread.c:254
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Sending NMI from CPU 1 to CPUs 0: