From: "Viktor Horvath" <duke586@hotmail.com>
[...]
Although some otherwise nice texts in the internet like this[1] claim that you don't need to have /dev/shm mounted to have named semaphores, at least my systems really needs it mounted. The second I unmounted it I got the familiar "function not implemented".
Sorry, forgot to mention the reference of [1]. It's http://archives.linuxfromscratch.org/mail-archives/lfs-dev/2003-October/039568.html