_lwp_sema_wait(2) System Calls _lwp_sema_wait(2)NAME
_lwp_sema_wait, _lwp_sema_trywait, _lwp_sema_init, _lwp_sema_post-
semaphore operations
SYNOPSIS
#include <sys/lwp.h>
int _lwp_sema_wait(lwp_sema_t *sema);
int _lwp_sema_trywait(lwp_sema_t *sema);
int _lwp_sema_init(lwp_sema_t *sema, int count);
int _lwp_sema_post(lwp_sema_t *sema);
DESCRIPTION
Conceptually, a semaphore is an non-negative integer count that is
atomically incremented and decremented. Typically this represents the
number of resources available. The _lwp_sema_init() function initial‐
izes the count, _lwp_sema_post() atomically increments the count, and
_lwp_sema_wait() waits for the count to become greater than 0 and then
atomically decrements it.
LWP semaphores must be initialized before use. The _lwp_sema_init()
function initializes the count associated with the LWP semaphore
pointed to by sema to count.
The _lwp_sema_wait() function blocks the calling LWP until the sema‐
phore count becomes greater than 0 and then atomically decrements it.
The _lwp_sema_trywait() function atomically decrements the count if it
is greater than zero. Otherwise it returns an error.
The _lwp_sema_post() function atomically increments the semaphore
count. If there are any LWPs blocked on the semaphore, one is
unblocked.
RETURN VALUES
Upon successful completion, 0 is returned. A non-zero value indicates
an error.
ERRORS
The _lwp_sema_init(), _lwp_sema_trywait(), _lwp_sema_wait(), and
_lwp_sema_post() functions will fail if:
EINVAL The sema argument points to an invalid semaphore.
EFAULT The sema argument points to an illegal address.
The _lwp_sema_wait() function will fail if:
EINTR The function execution was interrupted by a signal or fork(2).
The _lwp_sema_trywait() function will fail if:
EBUSY The function was called on a semaphore with a zero count.
The _lwp_sema_post() function will fail if:
EOVERFLOW The value of the sema argument exceeds SEM_VALUE_MAX.
SEE ALSOfork(2)SunOS 5.11 8 May 1998 _lwp_sema_wait(2)