msem_unlock(2)

DESCRIPTION

msem_unlock() unlocks a binary semaphore.

sem points to an msemaphore structure that specifies the semaphore to be unlocked.

If the condition argument is zero, the semaphore will be unlocked, whether or not any other processes are currently attempting to lock it. If the condition argument is MSEM_IF_WAITERS, and some other process is waiting to lock the semaphore or the implementation cannot reliably determine 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 is not unlocked and an error is returned.

All calls to msem_lock() and msem_unlock() 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 msem_init() followed by a (possibly empty) sequence of calls to msem_lock() and msem_unlock(), the results are undefined. The address of an msemaphore uniquely identifies the semaphore. If the msemaphore structure contains any value copied from a msemaphore structure at a different address, the result is undefined.

IMPLEMENTATION NOTES

The system attempts to ignore or recover from invalid values placed in the msemaphore structure, but this is not guaranteed for all cases.

RETURN VALUE

Upon success, msem_unlock() returns zero; otherwise, it returns -1 and sets errno to indicate the error.

ERRORS

msem_unlock() fails if any of the following conditions are encountered:

AUTHOR

msem_unlock() was developed by HP and OSF.

SEE ALSO

msem_init(2), msem_lock(2), msem_remove(2), mman(5).

STANDARDS CONFORMANCE

msem_unlock(): AES