The aiocbp argument points to the AIO control block to be canceled. if aiobcp is NULL, all outstanding cancelable AIO against fildes shall be canceled. Asynchronous notification shall occur for AIO that are successfully cancelled. Error status should be set to [ECANCELED] and return shall be -1 for successfully canceled AIO. aiocbp not successfully canceled shall not be modified aio_cancel() shall return AIO_CANCELED if the requested operations were canceled. aio_cancel() shall return AIO_NOTCANCELED if at least one of the requested operations cannot be canceled because it is in progress. aio_cancel() shall return AIO_ALLDONE if all operation have already completed aio_cancel() shall return -1 and set errno in all other case. aio_cancel() shall fail if: [EBADF] The fildes argument is not a valid descriptor.