INFO: task syz-executor.0:2121 blocked for more than 140 seconds. Not tainted 4.4.174+ #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D ffff8800a5c1f648 25344 2121 1 0x00000004 ffff8800a5c1f648 ffff8800b7d497c0 1075c530b5e6c507 ffff8800b7d497c0 0000000000000001 ffff8800b7d4a000 ffff8801db71f180 ffff8801db71f1a8 ffff8801db71e898 ffff8800b77e97c0 ffff8800b7d497c0 ffffed0014b83001 Call Trace: [] schedule+0x99/0x1d0 kernel/sched/core.c:3355 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3388 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x3c2/0xb80 kernel/locking/mutex.c:621 [] lo_open+0x1d/0xb0 drivers/block/loop.c:1633 [] __blkdev_get+0x2ae/0xdf0 fs/block_dev.c:1213 [] blkdev_get+0x2e8/0x920 fs/block_dev.c:1353 [] blkdev_open+0x1aa/0x250 fs/block_dev.c:1508 [] do_dentry_open+0x38f/0xbd0 fs/open.c:749 [] vfs_open+0x10b/0x210 fs/open.c:862 [] do_last fs/namei.c:3269 [inline] [] path_openat+0x136f/0x4470 fs/namei.c:3406 [] do_filp_open+0x1a1/0x270 fs/namei.c:3440 [] do_sys_open+0x2f8/0x600 fs/open.c:1038 [] SYSC_open fs/open.c:1056 [inline] [] SyS_open+0x2d/0x40 fs/open.c:1051 [] entry_SYSCALL_64_fastpath+0x1e/0x9a 2 locks held by syz-executor.0/2121: #0: (&bdev->bd_mutex){+.+.+.}, at: [] __blkdev_get+0x10c/0xdf0 fs/block_dev.c:1199 #1: (loop_index_mutex){+.+.+.}, at: [] lo_open+0x1d/0xb0 drivers/block/loop.c:1633 Sending NMI to all CPUs: NMI backtrace for cpu 0 CPU: 0 PID: 20 Comm: khungtaskd Not tainted 4.4.174+ #4 task: ffff8801da6c4740 task.stack: ffff8801d9ef0000 RIP: 0010:[] [] _flat_send_IPI_mask arch/x86/kernel/apic/apic_flat_64.c:62 [inline] RIP: 0010:[] [] flat_send_IPI_mask+0xf7/0x1b0 arch/x86/kernel/apic/apic_flat_64.c:69 RSP: 0018:ffff8801d9ef7c88 EFLAGS: 00000046 RAX: 0000000000000000 RBX: 0000000000000c00 RCX: 0000000000000000 RDX: 0000000000000c00 RSI: 0000000000000000 RDI: ffffffffff5fc300 RBP: ffff8801d9ef7cb8 R08: 0000000000000018 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000246 R13: 0000000003000000 R14: ffffffff82e5f2e0 R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff8801db600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000019a5000 CR3: 00000000b8b69000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: 0000000000000001 ffffffff82e5f2e0 ffffffff831a6ac0 fffffbfff0634c34 000000000001b6c0 0000000000000008 ffff8801d9ef7cd8 ffffffff81092bee 0000000000000008 ffffffff82924260 ffff8801d9ef7d30 ffffffff81ab8252 Call Trace: [] nmi_raise_cpu_backtrace+0x5e/0x80 arch/x86/kernel/apic/hw_nmi.c:33 [] nmi_trigger_all_cpu_backtrace.cold+0xa1/0xae 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+0xd3/0xee kernel/hung_task.c:238 [] kthread+0x273/0x310 kernel/kthread.c:211 [] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537 Code: 00 c3 5f ff 80 e6 10 75 e1 41 c1 e5 18 44 89 2c 25 10 c3 5f ff 44 89 fa 09 da 80 cf 04 41 83 ff 02 0f 44 d3 89 14 25 00 c3 5f ff <41> f7 c4 00 02 00 00 75 1e 4c 89 e7 57 9d 0f 1f 44 00 00 e8 f1 NMI backtrace for cpu 1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.4.174+ #4 task: ffff8801da6897c0 task.stack: ffff8801da698000 RIP: 0010:[] [] native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:53 RSP: 0018:ffff8801da69fd88 EFLAGS: 00000246 RAX: 0000000000000007 RBX: ffffffff8319bf68 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801da68a084 RBP: ffff8801da69fdb8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 R13: ffff8801da6a0000 R14: dffffc0000000000 R15: ffff8801da698000 FS: 0000000000000000(0000) GS:ffff8801db700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000019a33e0 CR3: 00000000b8d81000 CR4: 00000000001606b0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffffffff81020b16 ffff8801da698000 0000000000000000 ffff8801da6a0000 dffffc0000000000 ffff8801da698000 ffff8801da69fdc8 ffffffff81022d50 ffff8801da69fde0 ffffffff811eb4c8 0000000000000000 ffff8801da69fea8 Call Trace: [] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:423 [] default_idle_call+0x48/0x70 kernel/sched/idle.c:93 [] cpuidle_idle_call kernel/sched/idle.c:157 [inline] [] cpu_idle_loop kernel/sched/idle.c:253 [inline] [] cpu_startup_entry+0x6d1/0x810 kernel/sched/idle.c:301 [] start_secondary+0x31d/0x410 arch/x86/kernel/smpboot.c:245 Code: 2e 0f 1f 84 00 00 00 00 00 fa c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb c3 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 fb f4 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 f4 c3 0f 1f 40 00 66