From git bisect, I've found that http://git.savannah.gnu.org/cgit/libunwind.git/commit/?id=c90a2e02b3c1b03362a549a05261a4d0513d6026 fixes hung AFTER [ 341s] FAIL: Ltest-nocalloc [ 344s] PASS: Lrs-race [ 345s] PASS: run-check-namespace