Semaphore Subsystem

The Semaphore Subsystem implements the classic synchronization primitive. More...

Functions
syscall	wait (semaphore)
syscall	signal (semaphore)
syscall	signaln (semaphore, int)
semaphore	semcreate (int)
syscall	semfree (semaphore)
syscall	semcount (semaphore)

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Detailed Description

The Semaphore Subsystem implements the classic synchronization primitive.

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Function Documentation

syscall semcount

(

semaphore

sem

)

Return a semaphore's count.

Parameters:

sem	target semaphore

Returns:

count from semtab entry on success, SYSERR on failure

semaphore semcreate

(

int

count

)

Create and initialize a semaphore, returning its ID.

Parameters:

count

resources available.

Returns:

new semaphore ID on success, SYSERR on failure

syscall semfree

(

semaphore

sem

)

Deallocate a semaphore.

Reset the semaphore count, releasing any threads in the waiting queue. Deallocate entry in global semaphore table.

Parameters:

sem	target semaphore

Returns:

OK on success, SYSERR on failure

syscall signal

(

semaphore

sem

)

signal a semaphore, releasing one waiting thread

Parameters:

sem	target semaphore

Returns:

OK on success, SYSERR on failure

syscall signaln	(	semaphore	sem,
		int	count
	)

Signal a semaphore n times, releasing n waiting threads.

Parameters:

sem	target semaphore
count	number of times to signal

Returns:

OK on success, SYSERR on failure

syscall wait

(

semaphore

sem

)

Make current process wait on a semaphore.

Parameters:

sem	target semaphore

Returns:

OK on success, SYSERR on failure