Crash probably in libthr

[Grzegorz Blach]

On https://phab.enlightenment.org/T1330 I reported a crash in
Enlightenment. After analyzing backtraces from valgrind and gdb we think
this might be a bug in libthr.
Backtrace from valgrind:
https://phab.enlightenment.org/file/data/wlcvu7kmb5blxmgtnk2p/PHID-FILE-dimurhxlz4tvytoxnfup/valgrind2.log
Backtrace from gdb:
https://phab.enlightenment.org/file/data/zvbelqzjt4h3ppates6a/PHID-FILE-dsnaw3golsozpzlb7uqe/gdb2.log

Have any one known what
/usr/src/lib/libthr/arch/amd64/amd64/_umtx_op_err.S:37 does?