[Bug 1951033] Re: 20.04 SRU

[Michael Hudson-Doyle]

I verified part 3 of the test case, that (an appropriately configured)
unattended-upgrades upgrades an arm64 with libc6-lse without complaints:

new_user at ip-172-31-25-59:~/bench$ sudo unattended-upgrade   -v
Could not figure out development release: Distribution data outdated. Please check for an update for distro-info-data. See /usr/share/doc/distro-info-data/README.Debian for details.
Starting unattended upgrades script
Allowed origins are: o=Ubuntu,a=focal, o=Ubuntu,a=focal-security, o=UbuntuESMApps,a=focal-apps-security, o=UbuntuESM,a=focal-infra-security, o=Ubuntu,a=focal-updates, o=Ubuntu,a=focal-proposed, o=LP-PPA-mwhudson-devirt,a=focal
Initial blacklist: 
Initial whitelist (not strict): 
Packages that will be upgraded: libc-dev-bin libc6 libc6-dev libc6-lse
Writing dpkg log to /var/log/unattended-upgrades/unattended-upgrades-dpkg.log
Preconfiguring packages ...
Preconfiguring packages ...
(Reading database ... 169897 files and directories currently installed.)
Preparing to unpack .../libc6-lse_2.31-0ubuntu9.9_arm64.deb ...
Unpacking libc6-lse:arm64 (2.31-0ubuntu9.9) over (2.31-0ubuntu9.7) ...
Preparing to unpack .../libc6-dev_2.31-0ubuntu9.9_arm64.deb ...
Unpacking libc6-dev:arm64 (2.31-0ubuntu9.9) over (2.31-0ubuntu9.7) ...
Preparing to unpack .../libc-dev-bin_2.31-0ubuntu9.9_arm64.deb ...
Unpacking libc-dev-bin (2.31-0ubuntu9.9) over (2.31-0ubuntu9.7) ...
Preparing to unpack .../libc6_2.31-0ubuntu9.9_arm64.deb ...
Unpacking libc6:arm64 (2.31-0ubuntu9.9) over (2.31-0ubuntu9.7) ...
Setting up libc6:arm64 (2.31-0ubuntu9.9) ...
Setting up libc6-lse:arm64 (2.31-0ubuntu9.9) ...
Setting up libc-dev-bin (2.31-0ubuntu9.9) ...
Setting up libc6-dev:arm64 (2.31-0ubuntu9.9) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for libc-bin (2.31-0ubuntu9.9) ...
All upgrades installed

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https://bugs.launchpad.net/bugs/1951033

Title:
  20.04 SRU

Status in glibc package in Ubuntu:
  Fix Released
Status in glibc source package in Focal:
  Fix Committed

Bug description:
  [impact]
  It is time to update glibc in Focal. This bug is a placeholder for the overall process and a place to link the individual bugs that are being targeted:

   bug #1928508 Performance regression on memcpy() calls for AMD Zen
   bug #1899800 Runtime deadlock: pthread_cond_signal failed to wake up pthread_cond_wait due to a bug in undoing stealing
   bug #1892825 update-locale not perform correctly sanity checks
   bug #1918035 ld-2.31.so is not correctly packaged in libc6-dbg
   bug #1951032 AArch64: Backport memcpy improvements

  [test case]
  Each bug listed above has its own test case, of course. And glibc's own test case and the autopkgtests provide a good deal of assurance that things are working. But there are still some additional things we should test by hand.

  1. We should test upgrades interactively in a container and vm and make sure long running processes still function so you can still ssh in and a desktop session continues to operate as expected, ideally on a variety of architectures.
  2. We should build a core20 snap with the glibc from focal-proposed into a branch and test it with a variety of core20 snaps, on a variety of architectures.
  3. For arm64 specifically, we should test that upgrades of machines that do and do not have libc6-lse from 2.31-0ubuntu9.2 installed go smoothly.
  4. We should test graphical snaps with a variety of drivers (needs expansion!)

  [regression potential]
  Rebuilding glibc is always a little risky (toolchain bugs and incompatibilities between the old and new versions can be surprising).

  glibc's own tests and the autopkgtests that will be run should catch
  any regression in the new version of glibc itself.

  However, the biggest source of problems recently has been around
  upgrades and interactions between the old and new libcs, whether that
  is different versions of libc6 in a snap and its base or when an long
  running process has the older version mapped but interacts with
  artefacts from the newer version on disk. The tests in this bug are
  aimed at catching any of these problems before it gets to updates.

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