sem — POSIX semaphores

       The  sem  facility  provides  system  calls  used  by  the  standard  C library (libc) to implement POSIX
       semaphores.  This facility offers support for  such  functions  as  sem_init()  and  sem_wait().   It  is
       available both as a kernel option for static inclusion and as a dynamic kernel module.

       The sem facility appeared in FreeBSD 5.0.

Debian                                          February 7, 2014                                          SEM(4)

       sem — POSIX semaphores

sem_destroy(3),   sem_getvalue(3),   sem_init(3),   sem_open(3),   sem_post(3),  sem_wait(3),  config(8),
       kldload(8), kldunload(8)

       To compile this driver into the kernel, place the following line in your kernel configuration file:

             optionsP1003_1B_SEMAPHORES

       Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

             sem_load="YES"

       To load the driver as a module at run-time, run the following command as root:

             kldload sem