INFO: task blkid:15743 blocked for more than 140 seconds. Not tainted 4.4.140-ged9bdc8 #68 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. blkid D ffff8801b5b77a68 29088 15743 15738 0x00000004 ffff8801b5b77a68 0000000000000000 ffff8800b658d0e0 ffffed0016cb1a1b ffff8800b658c800 ffff8801db21fdb8 ffff8801db21fde0 ffff8801db21f4d8 ffff8801db21f4c0 ffff8800b6589800 ffff8800b658c800 0000000000000000 Call Trace: [] schedule+0x7a/0x1b0 kernel/sched/core.c:3359 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3392 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x307/0x850 kernel/locking/mutex.c:621 [] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355 [] __blkdev_driver_ioctl block/ioctl.c:288 [inline] [] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584 [] block_ioctl+0xde/0x120 fs/block_dev.c:1625 [] vfs_ioctl fs/ioctl.c:43 [inline] [] file_ioctl fs/ioctl.c:470 [inline] [] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605 [] SYSC_ioctl fs/ioctl.c:622 [inline] [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x22/0x9e 1 lock held by blkid/15743: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8b/0x1ad0 drivers/block/loop.c:1355 Sending NMI to all CPUs: NMI backtrace for cpu 0 CPU: 0 PID: 15741 Comm: syz-executor3 Not tainted 4.4.140-ged9bdc8 #68 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8800b6589800 task.stack: ffff8801d1ba0000 RIP: 0010:[] [] loop_set_fd drivers/block/loop.c:904 [inline] RIP: 0010:[] [] lo_ioctl+0x1682/0x1ad0 drivers/block/loop.c:1358 RSP: 0018:ffff8801d1ba7b98 EFLAGS: 00000286 RAX: 1ffff10038fa2e77 RBX: ffff8801ccaeb600 RCX: dffffc0000000000 RDX: 0000000000040000 RSI: ffffffff8251c642 RDI: ffff8801ccaeb750 RBP: ffff8801d1ba7c18 R08: ffff8800b658a128 R09: 0000000000000001 R10: 0000000000000000 R11: ffff8800b6589800 R12: ffff8800b9cca420 R13: ffff8800b9cc9cc0 R14: ffff8801d6a70000 R15: ffff8801d6a70158 FS: 00007f17540c2700(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0e0ad41f80 CR3: 00000001c7778000 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: 0000000b0000004c 0000000100000000 0000000000000000 ffff8801d6a70150 0000000000006000 0000000041b58ab3 ffff8800b9cca608 ffff8801c6df0400 ffff8800b9cc9db0 000000000002001d 0000000000000000 ffff8800b9cc9cc0 Call Trace: [] __blkdev_driver_ioctl block/ioctl.c:288 [inline] [] blkdev_ioctl+0x7b8/0x19c0 block/ioctl.c:584 [] block_ioctl+0xde/0x120 fs/block_dev.c:1625 [] vfs_ioctl fs/ioctl.c:43 [inline] [] file_ioctl fs/ioctl.c:470 [inline] [] do_vfs_ioctl+0x63f/0xf40 fs/ioctl.c:605 [] SYSC_ioctl fs/ioctl.c:622 [inline] [] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:613 [] entry_SYSCALL_64_fastpath+0x22/0x9e Code: 05 00 00 48 89 f8 48 c1 e8 03 80 3c 08 00 0f 85 8a 00 00 00 48 8b 9b 38 05 00 00 b9 ff ff 37 00 48 c1 e1 2a 48 8d bb 50 01 00 00 <48> 89 f8 48 c1 e8 03 0f b6 04 08 84 c0 0f 84 4d fe ff ff 3c 03 NMI backtrace for cpu 1 CPU: 1 PID: 491 Comm: khungtaskd Not tainted 4.4.140-ged9bdc8 #68 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffff8801d8ee1800 task.stack: ffff8800bb378000 RIP: 0010:[] [] native_apic_mem_write arch/x86/include/asm/apic.h:94 [inline] RIP: 0010:[] [] __default_send_IPI_dest_field arch/x86/include/asm/ipi.h:119 [inline] RIP: 0010:[] [] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:61 [inline] RIP: 0010:[] [] flat_send_IPI_mask+0xf6/0x1a0 arch/x86/kernel/apic/apic_flat_64.c:69 RSP: 0018:ffff8800bb37fcc8 EFLAGS: 00000046 RAX: 0000000003000000 RBX: 0000000000000c00 RCX: 0000000000000000 RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fb300 RBP: ffff8800bb37fcf0 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246 R13: 0000000000000003 R14: 0000000000000002 R15: ffffffff8446f6e0 FS: 0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001dfb000 CR3: 00000001d3a93000 CR4: 00000000001606f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff8446f6e0 ffffffff84a19060 0000000000000007 fffffbfff0942cbc 0000000000000040 ffff8800bb37fd10 ffffffff810b5f51 ffffffff83c0b760 0000000000000003 ffff8800bb37fd68 ffffffff81e19103 ffffffff8140ddaf Call Trace: [] nmi_raise_cpu_backtrace+0x61/0x80 arch/x86/kernel/apic/hw_nmi.c:33 [] nmi_trigger_all_cpu_backtrace.cold.4+0x70/0xad lib/nmi_backtrace.c:85 [] arch_trigger_all_cpu_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 [] trigger_all_cpu_backtrace include/linux/nmi.h:44 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog.cold.1+0xd3/0xee kernel/hung_task.c:238 [] kthread+0x268/0x300 kernel/kthread.c:211 [] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510 Code: b3 5f ff f6 c4 10 75 e2 44 89 e8 c1 e0 18 89 04 25 10 b3 5f ff 44 89 f2 09 da 80 cf 04 41 83 fe 02 0f 44 d3 89 14 25 00 b3 5f ff <41> f7 c4 00 02 00 00 75 1a 4c 89 e7 57 9d 0f 1f 44 00 00 e8 d2