INFO: task loop0:11102 blocked for more than 120 seconds. Not tainted 4.15.0-rc7+ #262 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. loop0 D24976 11102 2 0x80000000 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 schedule_timeout+0x1a3/0x230 kernel/time/timer.c:1769 io_schedule_timeout+0x26/0x80 kernel/sched/core.c:5030 do_wait_for_common kernel/sched/completion.c:86 [inline] __wait_for_common kernel/sched/completion.c:107 [inline] wait_for_common_io kernel/sched/completion.c:124 [inline] wait_for_completion_io+0x415/0x770 kernel/sched/completion.c:172 submit_bio_wait+0x13f/0x1e0 block/bio.c:947 blkdev_issue_flush+0x226/0x310 block/blk-flush.c:548 blkdev_fsync+0x86/0xb0 fs/block_dev.c:632 vfs_fsync_range+0x110/0x260 fs/sync.c:196 vfs_fsync+0x29/0x30 fs/sync.c:210 lo_req_flush drivers/block/loop.c:444 [inline] do_req_filebacked drivers/block/loop.c:572 [inline] loop_handle_cmd drivers/block/loop.c:1724 [inline] loop_queue_work+0x12a2/0x3900 drivers/block/loop.c:1738 kthread_worker_fn+0x32b/0x980 kernel/kthread.c:642 loop_kthread_worker_fn+0x51/0x60 drivers/block/loop.c:841 kthread+0x33c/0x400 kernel/kthread.c:238 ret_from_fork+0x37/0x50 arch/x86/entry/entry_64.S:530 Showing all locks held in the system: 2 locks held by khungtaskd/746: #0: (rcu_read_lock){....}, at: [<000000004ba213b5>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<000000004ba213b5>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000681f9e6f>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4464 1 lock held by rsyslogd/3503: #0: (&f->f_pos_lock){+.+.}, at: [<0000000057e874a5>] __fdget_pos+0x12b/0x190 fs/file.c:770 2 locks held by getty/3624: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3625: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3626: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3627: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3628: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3629: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/3630: #0: (&tty->ldisc_sem){++++}, at: [<00000000eed896a3>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000003df986e3>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor7/28591: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000001d5007fc>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 1 lock held by syz-executor7/28606: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<000000001d5007fc>] lo_ioctl+0x8b/0x1b70 drivers/block/loop.c:1355 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 746 Comm: khungtaskd Not tainted 4.15.0-rc7+ #262 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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.15.0-rc7+ #262 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:rcu_is_watching+0x23/0x110 kernel/rcu/tree.c:1156 RSP: 0018:ffff8801db207ac0 EFLAGS: 00000286 RAX: 0000000000000001 RBX: 1ffff1003b640f59 RCX: 0000000000000002 RDX: dffffc0000000000 RSI: ffffffff87037da0 RDI: ffffffff8682cbb4 RBP: ffff8801db207b40 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000040 R13: ffff8801db207b28 R14: ffffffff86809100 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000188dcd8 CR3: 0000000006822001 CR4: 00000000001606f0 Call Trace: rcu_read_lock_sched_held+0x8d/0x120 kernel/rcu/update.c:112 trace_softirq_entry include/trace/events/irq.h:128 [inline] __do_softirq+0x8fa/0xb85 kernel/softirq.c:284 invoke_softirq kernel/softirq.c:365 [inline] irq_exit+0x1cc/0x200 kernel/softirq.c:405 scheduler_ipi+0x318/0x820 kernel/sched/core.c:1803 smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277 reschedule_interrupt+0xa9/0xb0 arch/x86/entry/entry_64.S:950 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 RSP: 0018:ffffffff86807c38 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffffffff0d00f8a RCX: 0000000000000000 RDX: 1ffffffff0d19178 RSI: 0000000000000001 RDI: ffffffff868c8bc0 RBP: ffffffff86807c38 R08: ffffffff8666fae0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff86807cf0 R14: ffffffff87037da0 R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] default_idle+0xbf/0x460 arch/x86/kernel/process.c:355 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:346 default_idle_call+0x36/0x90 kernel/sched/idle.c:98 cpuidle_idle_call kernel/sched/idle.c:156 [inline] do_idle+0x24a/0x3b0 kernel/sched/idle.c:246 cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:351 rest_init+0xed/0xf0 init/main.c:436 start_kernel+0x7f1/0x819 init/main.c:716 x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378 x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 Code: 01 48 89 e5 5d c3 66 90 55 48 ba 00 00 00 00 00 fc ff df 48 89 e5 41 55 41 54 53 48 8d 5d 88 4c 8d 6d e8 48 c1 eb 03 48 83 ec 68 <48> c7 45 88 b3 8a b5 41 48 8d 04 13 48 c7 45 90 62 df 58 86 48