INFO: task syz-executor4:7428 blocked for more than 120 seconds. Not tainted 4.15.0-rc3+ #218 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor4 D20792 7428 3391 0x00000004 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_preempt_disabled+0x10/0x20 kernel/sched/core.c:3492 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 lo_open+0x1b/0xa0 drivers/block/loop.c:1571 __blkdev_get+0x2f9/0x10e0 fs/block_dev.c:1454 blkdev_get+0x3a1/0xad0 fs/block_dev.c:1591 blkdev_open+0x1e4/0x270 fs/block_dev.c:1749 do_dentry_open+0x682/0xd70 fs/open.c:752 vfs_open+0x107/0x230 fs/open.c:866 do_last fs/namei.c:3379 [inline] path_openat+0x1157/0x3530 fs/namei.c:3519 do_filp_open+0x25b/0x3b0 fs/namei.c:3554 do_sys_open+0x502/0x6d0 fs/open.c:1059 SYSC_open fs/open.c:1077 [inline] SyS_open+0x2d/0x40 fs/open.c:1072 entry_SYSCALL_64_fastpath+0x1f/0x96 RIP: 0033:0x40cd71 RSP: 002b:00007ff0cfd33780 EFLAGS: 00000293 ORIG_RAX: 0000000000000002 RAX: ffffffffffffffda RBX: 0000000020dbd000 RCX: 000000000040cd71 RDX: 0000000000000000 RSI: 0000000000000006 RDI: 00007ff0cfd33830 RBP: 0000000020dbd800 R08: 0000000000000000 R09: 0000000000000000 R10: 000000000000000c R11: 0000000000000293 R12: 000000000000001a R13: 0000000020dbc000 R14: 00007ff0cfd346d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/674: #0: (rcu_read_lock){....}, at: [<00000000a96ee4f2>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000a96ee4f2>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000a934f984>] debug_show_all_locks+0xd3/0x400 kernel/locking/lockdep.c:4554 2 locks held by getty/3120: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3121: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3122: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3123: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3124: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by getty/3125: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 2 locks held by syz-executor4/7428: #0: (&bdev->bd_mutex){+.+.}, at: [<000000005f92e340>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 #1: (loop_index_mutex){+.+.}, at: [<000000006e7714da>] lo_open+0x1b/0xa0 drivers/block/loop.c:1571 1 lock held by syz-executor4/7514: #0: (&bdev->bd_mutex){+.+.}, at: [<000000005f92e340>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 1 lock held by syz-executor2/7431: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bf075c5f>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor2/7447: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bf075c5f>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor2/7454: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bf075c5f>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor2/7457: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bf075c5f>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 1 lock held by syz-executor2/7469: #0: (&lo->lo_ctl_mutex/1){+.+.}, at: [<00000000bf075c5f>] lo_ioctl+0x8b/0x1b90 drivers/block/loop.c:1355 2 locks held by syz-executor1/7460: #0: (loop_index_mutex){+.+.}, at: [<00000000d76ba66d>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932 #1: (&lo->lo_ctl_mutex#2){+.+.}, at: [<0000000062da10ee>] loop_control_ioctl+0x1a7/0x490 drivers/block/loop.c:1946 1 lock held by syz-executor1/7475: #0: (loop_index_mutex){+.+.}, at: [<00000000d76ba66d>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932 1 lock held by syz-executor1/7483: #0: (loop_index_mutex){+.+.}, at: [<00000000d76ba66d>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932 1 lock held by syz-executor1/7490: #0: (loop_index_mutex){+.+.}, at: [<00000000d76ba66d>] loop_control_ioctl+0x89/0x490 drivers/block/loop.c:1932 2 locks held by getty/7517: #0: (&tty->ldisc_sem){++++}, at: [<00000000067fdb55>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000ab24f290>] n_tty_read+0x2f2/0x1a10 drivers/tty/n_tty.c:2131 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 674 Comm: khungtaskd Not tainted 4.15.0-rc3+ #218 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+0x37a/0x440 kernel/kthread.c:238 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:441 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.15.0-rc3+ #218 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:trace_lock_acquire include/trace/events/lock.h:13 [inline] RIP: 0010:lock_acquire+0x36c/0x580 kernel/locking/lockdep.c:4003 RSP: 0018:ffff8801db507b20 EFLAGS: 00000046 RAX: ffff8801d26b5b10 RBX: 0000000000000000 RCX: ffff8801d26b5b10 RDX: 1ffff1003a4d6b63 RSI: 1ffff1003a4d6b62 RDI: ffffffff85f2e480 RBP: ffff8801db507c18 R08: 0000000000000001 R09: 0000000000000000 R10: dffffc0000000000 R11: ffffffff81550630 R12: ffff8801d26b5b10 R13: 0000000000000000 R14: 0000000000000002 R15: 0000000000000001 FS: 0000000000000000(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f6b8cae3000 CR3: 00000001d0d09000 CR4: 00000000001426e0 DR0: 0000000020001000 DR1: 0000000020001000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline] read_seqcount_begin include/linux/seqlock.h:164 [inline] ktime_get+0x12f/0x3a0 kernel/time/timekeeping.c:762 tick_nohz_irq_enter kernel/time/tick-sched.c:1120 [inline] tick_irq_enter+0x9e/0x390 kernel/time/tick-sched.c:1141 irq_enter+0xbd/0xe0 kernel/softirq.c:346 scheduler_ipi+0x246/0x830 kernel/sched/core.c:1793 smp_reschedule_interrupt+0xe6/0x670 arch/x86/kernel/smp.c:277 reschedule_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:819 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 RSP: 0018:ffff8801da38fda8 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffff1003b471fb8 RCX: 0000000000000000 RDX: 1ffffffff0bd9734 RSI: 0000000000000001 RDI: ffffffff85ecb9a0 RBP: ffff8801da38fda8 R08: ffffffff85beaae8 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 R13: ffff8801da38fe60 R14: ffffffff865eb220 R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:93 [inline] default_idle+0xbf/0x460 arch/x86/kernel/process.c:348 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:339 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+0x18/0x20 kernel/sched/idle.c:351 start_secondary+0x330/0x460 arch/x86/kernel/smpboot.c:277 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237 Code: ff ff 49 ba 00 00 00 00 00 fc ff df 49 89 c4 49 8d 7c 24 08 48 89 fa 48 c1 ea 03 42 80 3c 12 00 0f 85 be 01 00 00 49 8b 7c 24 08 <4c> 89 95 18 ff ff ff 44 89 e9 ff 75 10 49 83 c4 18 53 45 89 f9