Since kernel 4.14.9, I have several machines that no longer boot. Both are showing rcu stalls. This problem occurs on a bare metal Intel i5 2500 system running Gentoo hardened with glibc, and also on KVM guests running Gentoo hardened musl. Downgrading to 4.14.8 makes the problem go away on both physical and virtual.
Created attachment 273299 [details] serial console output of a KVM guest with the problem
I'm rebooting the machine again with 4.14.9 to see if it will produce some more useful backtrace when giving it some more time before rebooting it.
Created attachment 273305 [details] serial console output of a KVM guest with the problem Unfortunately nothing useful yet after >2h "uptime"
same for me 4.14.8 boots without a problem i use an Intel(R) Core(TM) i5-2540M cpu
Created attachment 273307 [details] serial console output of a KVM guest with the problem with CONFIG_UNWINDER_FRAME_POINTER Previous logs were with CONFIG_UNWINDER_ORC=y. Still doesn't look very useful though, to me.
Reported this downstream @ https://bugs.gentoo.org/642268 and while debugging further, this might actually be a compiler bug. 4.14.9 compiled with GCC 6.4.0 results in this problem. The same version and config compiled with GCC 5.4.0 boots fine.
This bug is only reproducible with CONFIG_MCORE2=y
This has been fixed a long time ago.