A cooperative multitasker can ensure that there is no other task interacting between two invocations of pause. Pthreads however are really concurrent tasks (at least on a multi-core CPU), and therefore, several techniques to avoid conflicts when accessing the same resources.

Semaphores can only be aquired by one thread, all other threads have to wait until the semapohre is released.

semaphore ( "name" –  ) gforth-experimental “semaphore”

create a named semaphore name
name execution: ( – semaphore )

lock ( semaphore –  ) gforth-experimental “lock”

lock the semaphore

unlock ( semaphore –  ) gforth-experimental “unlock”

unlock the semaphore

The other approach to prevent concurrent access is the critical section. Here, we implement a critical section with a semaphore, so you have to specify the semaphore which is used for the critical section. Only those critical sections which use the same semaphore are mutually exclusive.

critical-section ( xt semaphore –  ) gforth-experimental “critical-section”

Execute xt while locking semaphore. After leaving xt, semaphore is unlocked even if an exception is thrown.