msem_lock(2)

DESCRIPTION

msem_lock() attempts to lock a binary semaphore.

sem points to an msemaphore structure which specifies the semaphore to be locked.

If the semaphore is not currently locked, it becomes locked and the function returns successfully.

If the semaphore is currently locked, and condition is MSEM_IF_NOWAIT, then the function returns with an error. If the semaphore is currently locked and condition is zero, the function does not return until either the calling process is able to successfully lock the semaphore, or an error condition occurs.

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 an msemaphore structure at a different address, the result is undefined.

IMPLEMENTATION NOTES

If blocked on a locked semaphore, msem_lock() suspends the calling process at a priority such that the process can be interrupted by a signal.

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

msem_lock() successfully acquires a semaphore that is locked by a process that has exited.

RETURN VALUE

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

ERRORS

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

AUTHOR

msem_lock() was developed by HP and OSF.

SEE ALSO

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

STANDARDS CONFORMANCE

msem_lock(): AES