pthread_spin_trylock( ) function shall lock the spin lock referenced by lock if it is not held by any thread. Otherwise, the function shall fail. Upon successful completion, these functions shall return zero; otherwise, an error number shall be returned to indicate the error. The pthread_spin_trylock( ) function shall fail if: [EBUSY] A thread currently holds the lock. These functions may fail if: [EINVAL] The value specified by lock does not refer to an initialized spin lock object. These functions shall not return an error code of EINTR.