INFO: task syz-executor4:10439 blocked for more than 120 seconds. Not tainted 4.15.0-rc8-next-20180116+ #98 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor4 D24176 10439 4735 0x80000000 Call Trace: context_switch kernel/sched/core.c:2845 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3421 schedule+0xf5/0x430 kernel/sched/core.c:3480 schedule_timeout+0x1a3/0x230 kernel/time/timer.c:1769 do_wait_for_common kernel/sched/completion.c:86 [inline] __wait_for_common kernel/sched/completion.c:107 [inline] wait_for_common kernel/sched/completion.c:118 [inline] wait_for_completion+0x415/0x770 kernel/sched/completion.c:139 exit_aio+0x463/0x520 fs/aio.c:903 __mmput kernel/fork.c:963 [inline] mmput+0x1b1/0x6c0 kernel/fork.c:987 exit_mm kernel/exit.c:544 [inline] do_exit+0x90a/0x1ad0 kernel/exit.c:856 do_group_exit+0x149/0x400 kernel/exit.c:972 SYSC_exit_group kernel/exit.c:983 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:981 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x452df9 RSP: 002b:0000000000a2fa08 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000071bec8 RCX: 0000000000452df9 RDX: 0000000000000000 RSI: 0000000000720a28 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000286 R10: 000000000000000a R11: 0000000000000202 R12: 0000000000a2f9b0 R13: 000000000071bea0 R14: 0000000000000170 R15: 000000000000000a Showing all locks held in the system: 2 locks held by khungtaskd/750: #0: (rcu_read_lock){....}, at: [<00000000e4bdfcff>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000e4bdfcff>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000008491b9ad>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 2 locks held by getty/3637: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3638: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3639: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3640: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3641: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3642: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/10473: #0: (&tty->ldisc_sem){++++}, at: [<000000006f1fd26c>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<0000000051109b9e>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 750 Comm: khungtaskd Not tainted 4.15.0-rc8-next-20180116+ #98 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 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:138 [inline] check_hung_task kernel/hung_task.c:132 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline] watchdog+0x90c/0xd60 kernel/hung_task.c:249 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x37/0x50 arch/x86/entry/entry_64.S:530 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54