MSEM_UNLOCK(3)                       SysV                       MSEM_UNLOCK(3)



NAME
     msem_unlock - Unlock a semaphore

SYNOPSIS
     #include <sys/mman.h>

     int msem_unlock (sem, condition )
     msemaphore *sem;
     int condition;

DESCRIPTION
     The msem_unlock function unlocks a binary semaphore.

     The sem argument points to an msemaphore structure which specifies the
     semaphore to be unlocked.

     If the condition argument is 0 (zero), the semaphore is unlocked, whether
     or not any other processes are currently attempting to lock it.  If the
     condition argument is MSEM_IF_WAITERS, and another process is waiting to
     lock the semaphore or it cannot be reliably determined whether some
     process is waiting to lock the semaphore, the semaphore is unlocked by
     the calling process.  If the condition argument is MSEM_IF_WAITERS, and
     no process is waiting to lock the semaphore, the semaphore will not be
     unlocked and an error will be returned.

     All calls to the msem_lock(3) and msem_unlock functions by multiple
     processes sharing a common msemaphore structure behave as if the calls
     were serialized.

     If the msemaphore structure contains any value not resulting from a call
     to the msem_init(3) function followed by a (possibly empty) sequence of
     calls to the msem_lock(3) and msem_unlock functions, the results are
     undefined.  The address of an msemaphore structure may be significant.
     If the msemaphore structure contains any value copied from an msemaphore
     structure at a different address, the result is undefined.

DIAGNOSTICS
     On successful completion, the msem_unlock function returns 0 (zero).  On
     error, the msem_unlock function returns -1 and sets errno to indicate the
     error.

ERRORS
     msem_unlock fails if:

     [EAGAIN]       MSEM_IF_WAITERS was specified and there were no waiters.

     [EINVAL]       The sem argument points to an msemaphore structure which
                    specifies a semaphore which has been removed, or the
                    condition argument is invalid.

SEE ALSO
     msem_init(3), msem_lock(3), msem_remove(3), <sys/mman.h>