Semaphores

Counting semaphores are available as an alternative primitive for managing threads within device drivers. See the semaphore(9F) man page for more information. The semaphore functions are:

sema_destroy(9F)

Destroys a semaphore.

sema_init(9F)

Initialize a semaphore.

sema_p(9F)

Decrement semaphore and possibly block.

sema_p_sig(9F)

Decrement semaphore but do not block if signal is pending. See Threads Unable to Receive Signals.

sema_tryp(9F)

Attempt to decrement semaphore, but do not block.

sema_v(9F)

Increment semaphore and possibly unblock waiter.