Can anyone help to shed the light on mysterious bug in SBCL (found it!)

[Matthew Dillon]

    I have committed a mitigation to libthread_xu in master.  It will
    munmap the red-zone and any cached thread stacks on unload and avoid
    the panic.

    I'm not entirely sure whether rtld-elf will safely unwind libc bindings
    and other weak symbol overrides, though.  libc also has some persistent
    state related to threading that might get compromised, so I don't know
    if this will work 100%.

    I still think the correct solution is to not unload libraries not
    designed to be unloadable.

						-Matt