Comment 0 for bug 1868272

Bind just released 9.16.1. Focal has 9.16.0. This release was expected and is considered important, as it's the first point release after a new major one, and we should have it in focal.

Release notes: https://downloads.isc.org/isc/bind9/9.16.1/RELEASE-NOTES-bind-9.16.1.html

More detailed notes: https://gitlab.isc.org/isc-projects/bind9/-/blob/v9_16/CHANGES (look in the 9.16.1 section)

The one change that is indeed a feature change, and not a bug fix, is mentioned in the release notes only:
"""
Feature Changes

    The system-provided POSIX Threads read-write lock implementation is now used by default instead of the native BIND 9 implementation. Please be aware that glibc versions 2.26 through 2.29 had a bug that could cause BIND 9 to deadlock. A fix was released in glibc 2.30, and most current Linux distributions have patched or updated glibc, with the notable exception of Ubuntu 18.04 (Bionic) which is a work in progress. If you are running on an affected operating system, compile BIND 9 with --disable-pthread-rwlock until a fixed version of glibc is available. [GL !3125]
"""

The linked upstream glibc bug[1] still affects[2] bionic, and bionic only. I prepared an SRU for it, but I'm out of my depth on that one. I basically grabbed the patch, test case, and confirmed the test case no longer locks up with the patch applied.

Focal doesn't have that bug, but it's still worth to call out this change. It's upstream's new default, so they must have good reasoning for it. I emailed[3] the bind-users@ mailing list asking if they have more details on what that change means, or why it was made.

We can always disable it, by passing --disable-pthread-rwlock.

PPA with test packages (where I did *NOT* pass --disable-pthread-rwlock, i.e., it's using upstream's default): https://launchpad.net/~ci-train-ppa-service/+archive/ubuntu/3984/

Bileto ticket with green tests (bar i386, known): https://bileto.ubuntu.com/#/ticket/3984