INFO: task syz-executor.2:5551 blocked for more than 140 seconds. Not tainted 4.9.194+ #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D25464 5551 1 0x00000004 0000000000000083 ffff8801d9804740 ffff8801d3017380 ffff8801db721000 ffff8801d3b1c740 ffff8801db721018 ffff88019d8f7688 ffffffff8281af8e ffffffff81bcd65c ffffffff841f8b40 000060fe2460d0a0 ffff8801db7218f0 Call Trace: [<00000000574564a5>] schedule+0x92/0x1c0 kernel/sched/core.c:3546 [<00000000b27bd9f1>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3579 [<00000000ed34d5e6>] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [<00000000ed34d5e6>] mutex_lock_nested+0x38d/0x920 kernel/locking/mutex.c:621 [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 [<000000001fb7965f>] __blkdev_get+0x268/0xeb0 fs/block_dev.c:1287 [<0000000043f3e016>] blkdev_get+0x2e8/0x920 fs/block_dev.c:1424 [<0000000051d96ab9>] blkdev_open+0x1aa/0x250 fs/block_dev.c:1579 [<00000000631db6d0>] do_dentry_open+0x422/0xd20 fs/open.c:791 [<000000009eca0c5c>] vfs_open+0x105/0x230 fs/open.c:904 [<000000007fd67196>] do_last fs/namei.c:3541 [inline] [<000000007fd67196>] path_openat+0xbf5/0x2f60 fs/namei.c:3665 [<00000000977e42d6>] do_filp_open+0x1a1/0x280 fs/namei.c:3699 [<00000000fa936ce5>] do_sys_open+0x2f0/0x610 fs/open.c:1097 [<00000000eddac90f>] SYSC_open fs/open.c:1115 [inline] [<00000000eddac90f>] SyS_open+0x2d/0x40 fs/open.c:1110 [<0000000086da2e51>] do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288 [<00000000704b2ad7>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/24: #0: (rcu_read_lock){......}, at: [<00000000febb7b9a>] check_hung_uninterruptible_tasks kernel/hung_task.c:169 [inline] #0: (rcu_read_lock){......}, at: [<00000000febb7b9a>] watchdog+0x14b/0xaf0 kernel/hung_task.c:263 #1: (tasklist_lock){.+.+..}, at: [<000000009176e3b7>] debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4336 2 locks held by getty/2031: #0: (&tty->ldisc_sem){++++++}, at: [<0000000091f5dc36>] ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+...}, at: [<000000009a89bbf5>] n_tty_read+0x1fe/0x1820 drivers/tty/n_tty.c:2156 2 locks held by syz-executor.2/5551: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006dfe02ca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.3/7245: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006dfe02ca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.1/11422: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006dfe02ca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.4/11744: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006dfe02ca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 2 locks held by syz-executor.0/13071: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [<0000000008a5a608>] lo_ioctl+0x8e/0x1b10 drivers/block/loop.c:1404 #1: (&bdev->bd_mutex){+.+.+.}, at: [<00000000c83a8add>] blkdev_reread_part+0x1f/0x40 block/ioctl.c:189 2 locks held by syz-executor.5/13079: #0: (loop_index_mutex){+.+.+.}, at: [<00000000b9822699>] loop_control_ioctl+0x7a/0x320 drivers/block/loop.c:1973 #1: (&lo->lo_ctl_mutex#2){+.+.+.}, at: [<0000000045dfd24d>] loop_control_ioctl+0x17f/0x320 drivers/block/loop.c:1987 2 locks held by blkid/13080: #0: (&bdev->bd_mutex){+.+.+.}, at: [<000000006dfe02ca>] __blkdev_get+0x10e/0xeb0 fs/block_dev.c:1273 #1: (loop_index_mutex){+.+.+.}, at: [<000000001403f364>] lo_open+0x1d/0xb0 drivers/block/loop.c:1621 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 24 Comm: khungtaskd Not tainted 4.9.194+ #0 ffff8801d98d7cc8 ffffffff81b67001 0000000000000001 0000000000000000 0000000000000001 ffffffff81099d01 dffffc0000000000 ffff8801d98d7d00 ffffffff81b7229c 0000000000000001 0000000000000000 0000000000000001 Call Trace: [<000000003a79c256>] __dump_stack lib/dump_stack.c:15 [inline] [<000000003a79c256>] dump_stack+0xc1/0x120 lib/dump_stack.c:51 [<00000000a0ab0e21>] nmi_cpu_backtrace.cold+0x47/0x87 lib/nmi_backtrace.c:99 [<00000000fafca868>] nmi_trigger_cpumask_backtrace+0x124/0x155 lib/nmi_backtrace.c:60 [<000000007f1ca087>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [<000000001b43cedb>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [<000000001b43cedb>] check_hung_task kernel/hung_task.c:126 [inline] [<000000001b43cedb>] check_hung_uninterruptible_tasks kernel/hung_task.c:183 [inline] [<000000001b43cedb>] watchdog+0x670/0xaf0 kernel/hung_task.c:263 [<00000000ca93d6ac>] kthread+0x278/0x310 kernel/kthread.c:211 [<0000000048320701>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff8282a0e1