MFC r321082: Add regression tests for bugs 220459 and 220398 Bug 220398 - lio_listio(2) never sends asynchronous notification if nent==0 Bug 220459 - lio_listio(2) doesn't support SIGEV_THREAD PR: 220459 PR: 220398 Reviewed by: cem, jhb Sponsored by: Spectra Logic Corp Differential Revision: https://reviews.freebsd.org/D11470