armv7-on-aarch64 stuck at urdlck

I don't want to hijack the original thread, so I'm replying in a new one.

My tegra track current, has been running 24/7 by building kernel/world 
and kde5 in a loop for a few years now. But I have never encountered the 
aforementioned lockup in native armv7.

I have seen usermode mutex lockup in arm32 jail on aarch64, but only 
very rarely (once a month or so) and all my attempts to reproduce it in 
a more deterministic way have failed. Also, I don't think I've ever seen 
this with the debug version of libc.

Unfortunately I also failed to reproduce given lockup using 
dlopen_test.c, neither on native armv7 or arm32 jail.

Michal Meloun