This is xnu-8019. See this file in:
Directory listing for xnu-8019//libsyscall/wrappers/cancelable
fcntl-base.c
fcntl-cancel.c
fcntl.c
open.c
pselect-darwinext-cancel.c
pselect-darwinext.c
select-cancel.c
select.c
sigsuspend-cancel.c
sigsuspend.c