INFO: task syz-executor.1:31328 blocked for more than 140 seconds. Not tainted 4.9.141+ #23 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D28888 31328 31325 0x20020000 ffff88015850c740 ffff8801ceddc780 ffff8801a5f7ee00 ffff8801c6ee8000 ffff8801db721018 ffff8801cac27b50 ffffffff828075c2 0000000000000000 ffffffff83ce73a0 ffff8801cac27da0 0000000000000829 ffff8801db7218f0 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3553 [] schedule_timeout+0x735/0xe20 kernel/time/timer.c:1771 [] down_read_failed drivers/tty/tty_ldsem.c:241 [inline] [] __ldsem_down_read_nested+0x33c/0x610 drivers/tty/tty_ldsem.c:332 [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 [] tty_ldisc_ref_wait+0x25/0x80 drivers/tty/tty_ldisc.c:275 [] tty_compat_ioctl+0x12d/0x270 drivers/tty/tty_io.c:3039 [] C_SYSC_ioctl fs/compat_ioctl.c:1602 [inline] [] compat_SyS_ioctl+0x12d/0x1fd0 fs/compat_ioctl.c:1549 [] do_syscall_32_irqs_on arch/x86/entry/common.c:328 [inline] [] do_fast_syscall_32+0x2f1/0xa10 arch/x86/entry/common.c:390 [] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137 Showing all locks held in the system: 2 locks held by khungtaskd/24: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11c/0xa20 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336 1 lock held by rsyslogd/1900: #0: (&f->f_pos_lock){+.+.+.}, at: [] __fdget_pos+0xac/0xd0 fs/file.c:781 2 locks held by getty/2027: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142 2 locks held by syz-executor.1/31325: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+.+.}, at: [] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142 1 lock held by syz-executor.1/31328: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 1 lock held by syz-executor.1/3113: #0: (&pipe->mutex/1){+.+.+.}, at: [] __pipe_lock fs/pipe.c:87 [inline] #0: (&pipe->mutex/1){+.+.+.}, at: [] pipe_release+0x50/0x250 fs/pipe.c:568 1 lock held by syz-executor.1/3115: #0: (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock_nested fs/pipe.c:66 [inline] #0: (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock+0x5e/0x70 fs/pipe.c:74 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.141+ #23 ffff8801d9907d08 ffffffff81b42e79 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810983b0 ffff8801d9907d40 ffffffff81b4df89 0000000000000001 0000000000000000 0000000000000003 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6ad/0xa20 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff82816496