==================================== kobject: 'loop4' (00000000b050627d): kobject_uevent_env kobject: 'loop4' (00000000b050627d): fill_kobj_path: path = '/devices/virtual/block/loop4' ------------[ cut here ]------------ downgrading a read lock WARNING: CPU: 0 PID: 15784 at kernel/locking/lockdep.c:3556 __lock_downgrade kernel/locking/lockdep.c:3556 [inline] WARNING: CPU: 0 PID: 15784 at kernel/locking/lockdep.c:3556 lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3819 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 15784 Comm: blkid Not tainted 4.20.0-rc4+ #255 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 panic+0x2ad/0x55c kernel/panic.c:188 __warn.cold.8+0x20/0x45 kernel/panic.c:540 report_bug+0x254/0x2d0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969 RIP: 0010:__lock_downgrade kernel/locking/lockdep.c:3556 [inline] RIP: 0010:lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3819 Code: 00 00 fc ff df 41 c6 44 05 00 f8 e9 1b ff ff ff 48 c7 c7 60 68 2b 88 4c 89 9d 58 ff ff ff 48 89 85 60 ff ff ff e8 d9 1f e7 ff <0f> 0b 48 8b 85 60 ff ff ff 4c 8d 4d d8 4c 89 e9 48 ba 00 00 00 00 RSP: 0018:ffff8881d8817b70 EFLAGS: 00010086 RAX: 0000000000000000 RBX: 1ffff1103b102f74 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff8165eaf5 RDI: 0000000000000006 RBP: ffff8881d8817c28 R08: ffff8881d1a16140 R09: fffffbfff12b2254 R10: fffffbfff12b2254 R11: ffffffff895912a3 R12: ffffffff8b0f67a0 R13: ffff8881d8817bc0 R14: 0000000000000001 R15: ffff8881d1a16140 downgrade_write+0x76/0x270 kernel/locking/rwsem.c:147 __do_munmap+0xcd8/0xf80 mm/mmap.c:2812 __vm_munmap+0x138/0x1f0 mm/mmap.c:2837 __do_sys_munmap mm/mmap.c:2862 [inline] __se_sys_munmap mm/mmap.c:2859 [inline] __x64_sys_munmap+0x65/0x80 mm/mmap.c:2859 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fae50695417 Code: f0 ff ff 73 01 c3 48 8d 0d 8a ad 20 00 31 d2 48 29 c2 89 11 48 83 c8 ff eb eb 90 90 90 90 90 90 90 90 90 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8d 0d 5d ad 20 00 31 d2 48 29 c2 89 RSP: 002b:00007ffdabcf1618 EFLAGS: 00000203 ORIG_RAX: 000000000000000b RAX: ffffffffffffffda RBX: 00007fae508a01c8 RCX: 00007fae50695417 RDX: 0000000000126b00 RSI: 00000000000033ef RDI: 00007fae50898000 RBP: 00007ffdabcf1780 R08: 0000000000000001 R09: 0000000000000007 R10: 00007fae5068fa0b R11: 0000000000000203 R12: 000000009a56330f R13: 000000a29a56330f R14: 000000a29a456c0b R15: 00007fae50895740 Kernel Offset: disabled Rebooting in 86400 seconds..