x86/split lock detection

[pmhahn]

Running remake 4.3 (4.3+dbg-1.5+dfsg-1) on Ubuntu 22.04 triggers Linux kernel warnings:

[ +19,619040] x86/split lock detection: #DB: remake/737636 took a bus_lock trap at address: 0x5555555645d6
[  +0,118315] x86/split lock detection: #DB: remake/737639 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,005202] x86/split lock detection: #DB: remake/737644 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,004291] x86/split lock detection: #DB: remake/737648 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,002163] x86/split lock detection: #DB: remake/737650 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,002555] x86/split lock detection: #DB: remake/737652 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,012782] x86/split lock detection: #DB: remake/737665 took a bus_lock trap at address: 0x7ffff7b26840
[  +0,019462] x86/split lock detection: #DB: remake/737685 took a bus_lock trap at address: 0x7ffff7b26840

See https://lwn.net/Articles/911219/ for some background.

Sadly I cannot pinpoint exactly which atomic action triggers the warning. I'll try running with split_lock_detect=fatal after the next reboot to get remake killed SIGBUS and using gdb to find the exact location