xref: /illumos-gate/usr/src/man/man2/_lwp_sema_wait.2 (revision bbf215553c7233fbab8a0afdf1fac74c44781867)
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_LWP_SEMA_WAIT 2 "May 8, 1998"
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 initializes 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 semaphore 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 ALSO

fork (2)