INFO: task hung in seq_free

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
android-49	INFO: task hung in seq_free_client				2	2068d	2174d	0/3	auto-closed as invalid on 2019/02/23 15:39
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
INFO: task syz-executor7:15804 blocked for more than 140 seconds.
      Not tainted 4.18.0-rc8+ #32
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor7   D14640 15804   4045 0x00000006
Call Trace:
 context_switch kernel/sched/core.c:2857 [inline]
 __schedule+0x62a/0x870 kernel/sched/core.c:3507
 schedule kernel/sched/core.c:3551 [inline]
 schedule_preempt_disabled+0x57/0x80 kernel/sched/core.c:3609
 __mutex_lock_common kernel/locking/mutex.c:834 [inline]
 __mutex_lock+0x1ed/0x420 kernel/locking/mutex.c:894
 __mutex_lock_slowpath+0xe/0x10 kernel/locking/mutex.c:1155
 mutex_lock+0x34/0x40 kernel/locking/mutex.c:242
 seq_free_client+0x1b/0xb0 sound/core/seq/seq_clientmgr.c:277
 snd_seq_release+0x23/0x70 sound/core/seq/seq_clientmgr.c:367
 __fput+0x110/0x280 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0xb4/0xe0 kernel/task_work.c:113
 get_signal+0x888/0x8c0 kernel/signal.c:2298
 do_signal+0x23/0x550 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop arch/x86/entry/common.c:162 [inline]
 prepare_exit_to_usermode+0xe0/0x170 arch/x86/entry/common.c:197
 syscall_return_slowpath+0x3f/0x270 arch/x86/entry/common.c:268
 do_syscall_64+0x6d/0x90 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x456d89
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007f39008d4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 00007f39008d56d4 RCX: 0000000000456d89
RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00000000009301e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d2ea8 R14: 00000000004c74aa R15: 0000000000000002
NMI backtrace for cpu 0
CPU: 0 PID: 677 Comm: khungtaskd Not tainted 4.18.0-rc8+ #32
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+0xae/0xf0 lib/dump_stack.c:113
 nmi_cpu_backtrace lib/nmi_backtrace.c:103 [inline]
 nmi_trigger_cpumask_backtrace+0xdd/0x1e0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x10/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace+0x17/0x20 include/linux/nmi.h:138
 check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline]
 watchdog+0x4be/0x4d0 kernel/hung_task.c:252
 kthread+0x127/0x140 kernel/kthread.c:247
 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:55 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:97 [inline]
NMI backtrace for cpu 1 skipped: idling at default_idle+0x76/0xf0 arch/x86/kernel/process.c:500