[Bug 1912652] Re: Upgrading libc6-lse breaks on systems it is in use

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: glibc (Ubuntu Bionic)
       Status: New => Confirmed

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https://bugs.launchpad.net/bugs/1912652

Title:
  Upgrading libc6-lse breaks on systems it is in use

Status in glibc package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader package in Ubuntu:
  Confirmed
Status in glibc source package in Bionic:
  Confirmed
Status in ubuntu-release-upgrader source package in Bionic:
  Confirmed
Status in glibc source package in Focal:
  Fix Committed
Status in ubuntu-release-upgrader source package in Focal:
  Confirmed
Status in glibc source package in Groovy:
  Fix Committed
Status in ubuntu-release-upgrader source package in Groovy:
  Confirmed
Status in glibc source package in Hirsute:
  Fix Released
Status in ubuntu-release-upgrader source package in Hirsute:
  Confirmed

Bug description:
  [Impact]

   * On arm64 systems supporting LSE and libc6-lse being installed an attempt to upgrade the package makes the upgrade fail and leave the system in an unusable state.
   * Performing a release upgrade on such arm64 systems also break if the libc6-lse package was installed and it is also present in the target release.

  [Test Plan (Focal)]

   * Set up an 8 core LSE system such as one of the AWS Graviton2 instances.
   * If libc6-lse is installed, remove it.
   * Compile and run the a.c test program attached in LP: #1885012 and measure the run time a few times.
     gcc -O2 -o a.out a.c -lpthread -DITER=1000 -DTHREADS=64
   * Install libc6-lse (again).
   * Reboot
   * Upgrade to the fixed libc6 package which Provides libc6-lse.
   * The upgrade should succeed and remove the libc6-lse package.
   * Run the compiled a.c again and observe it running much faster than with the standard libc6 package.

  [Test Plan (Groovy)]

   * Groovy's libc6 is already compiled with -moutline-atomics by default, thus there is no need to verify that.
   * Set up an LSE system such as one of the AWS Graviton2 instances.
   * Install libc6-lse if it is not installed.
   * Reboot
   * Upgrade to the fixed libc6 package which Provides libc6-lse.
   * The upgrade should succeed and automatically remove the libc6-lse package.

  [Where problems could occur]

  * The fix is compiling libc6 with -moutline-atomics which is in use
  instead of shipping the libc6-lse separate binary package. Should
  there be any GCC bug it could cause problems.

  [Other Info (Focal)]

  * The positive side effect of merging libc6-lse to libc6 and enabling
  optimization is that on capable HW the default libc6 will take
  advantage of the LSE instructions and improve the performance without
  requiring the installation of the additional libc libraries.

  [Original Bug Text]

  Errors were encountered while processing:
   /var/cache/apt/archives/libc6_2.32-0ubuntu3_arm64.deb
  Exception during pm.DoInstall():  E:Sub-process /usr/bin/dpkg returned an error code (1)

  ProblemType: Package
  DistroRelease: Ubuntu 20.04
  Package: libc6 2.31-0ubuntu9.1
  ProcVersionSignature: Ubuntu 5.4.0-1035.37-aws 5.4.78
  Uname: Linux 5.4.0-1035-aws aarch64
  ApportVersion: 2.20.11-0ubuntu27.14
  Architecture: arm64
  CasperMD5CheckResult: skip
  Date: Thu Jan 21 16:19:53 2021
  Df:

  Dmesg:

  Ec2AMI: ami-0489277f0e9a94f8d
  Ec2AMIManifest: (unknown)
  Ec2AvailabilityZone: eu-central-1c
  Ec2InstanceType: t4g.micro
  Ec2Kernel: unavailable
  Ec2Ramdisk: unavailable
  ErrorMessage: new libc6:arm64 package post-removal script subprocess returned error exit status 127
  Python3Details: /usr/bin/python3.8, Python 3.8.5, python3-minimal, 3.8.2-0ubuntu2
  PythonDetails: N/A
  RelatedPackageVersions:
   dpkg 1.19.7ubuntu3
   apt  2.0.2ubuntu0.2
  SourcePackage: glibc
  Title: package libc6 2.31-0ubuntu9.1 failed to install/upgrade: new libc6:arm64 package post-removal script subprocess returned error exit status 127
  UpgradeStatus: Upgraded to focal on 2021-01-21 (0 days ago)

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