------------[ cut here ]------------ downgrading a read lock WARNING: CPU: 0 PID: 9300 at kernel/locking/lockdep.c:3553 __lock_downgrade kernel/locking/lockdep.c:3553 [inline] WARNING: CPU: 0 PID: 9300 at kernel/locking/lockdep.c:3553 lock_downgrade+0x4d2/0x910 kernel/locking/lockdep.c:3816 Kernel panic - not syncing: panic_on_warn set ... CPU: 0 PID: 9300 Comm: blkid Not tainted 4.20.0-next-20190107 #6 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+0x1db/0x2d0 lib/dump_stack.c:113 panic+0x2cb/0x65c kernel/panic.c:214 __warn.cold+0x20/0x48 kernel/panic.c:571 report_bug+0x263/0x2b0 lib/bug.c:186 fixup_bug arch/x86/kernel/traps.c:178 [inline] fixup_bug arch/x86/kernel/traps.c:173 [inline] do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973 RIP: 0010:__lock_downgrade kernel/locking/lockdep.c:3553 [inline] RIP: 0010:lock_downgrade+0x4d2/0x910 kernel/locking/lockdep.c:3816 Code: 00 00 00 fc ff df 41 c6 04 06 f8 e9 1f ff ff ff 48 c7 c7 c0 a7 4b 88 4c 89 8d 58 ff ff ff 48 89 85 60 ff ff ff e8 fe 13 e7 ff <0f> 0b 48 8b 85 60 ff ff ff 4c 8d 5d d8 4c 89 f1 48 ba 00 00 00 00 RSP: 0018:ffff8880569dfbb8 EFLAGS: 00010082 RAX: 0000000000000000 RBX: 1ffff1100ad3bf7d RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff81686376 RDI: 0000000000000006 RBP: ffff8880569dfc70 R08: ffff888057b52040 R09: fffffbfff1333299 R10: fffffbfff1333298 R11: ffffffff899994c3 R12: ffff888057b52040 R13: ffffffff8b56ca20 R14: ffff8880569dfc08 R15: 0000000000000001 downgrade_write+0x76/0x270 kernel/locking/rwsem.c:147 __do_munmap+0xc5a/0xef0 mm/mmap.c:2823 __vm_munmap+0x139/0x1f0 mm/mmap.c:2848 __do_sys_munmap mm/mmap.c:2873 [inline] __se_sys_munmap mm/mmap.c:2870 [inline] __x64_sys_munmap+0x67/0x80 mm/mmap.c:2870 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f1b3499b417 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:00007ffe6aa86bd8 EFLAGS: 00000203 ORIG_RAX: 000000000000000b RAX: ffffffffffffffda RBX: 00007f1b34ba61c8 RCX: 00007f1b3499b417 RDX: 0000000000111500 RSI: 00000000000033ef RDI: 00007f1b34b9e000 RBP: 00007ffe6aa86d40 R08: 0000000000000001 R09: 0000000000000007 R10: 00007f1b34995a0b R11: 0000000000000203 R12: 00000000be9bc666 R13: 0000008fbe9bc666 R14: 0000008fbe8ced05 R15: 00007f1b34b9b740 Kernel Offset: disabled Rebooting in 86400 seconds..