[Bug 1901343] [NEW] timing bug creates interacctions between util-linux utitlities

[Kevin O'Gorman]

Public bug reported:

This is a creepy bug that seems to disappear under examination.  In this
case it appears that the bug is a timing bug, and introducing delays
makes it go away.  I call this sort of thing a "frankenbug" because of
creepyness and difficulty diagnosing.

It appears to be an interaction between a call to sfdisk(8) and a
subsequent call to lsblk(8).  I have a test script that displays the bug
on my systems under the right circumstances -- in particular, on my core
i-7 Dell 990, it shows up when reporting on a USB 3.0 GPT stick, but not
when reporting on the boot drive /dev/sda formatted with MBR.

This is a much simplified program, derived from a backup utility I've
been working on.  You can run it with no delays (default) or introduce
delays with the -z (sleep 1) switch or the -y (sync) switch.  The
correct output occurs with the -z switch.  In the others, the partition
types are not reported.  There should be no difference.

Example runs:

root at giggles:~/bin# bash test.sh sdd
label: gpt
ptv[@] is ""
ftv[@] is "ext4 swap  vfat ext4 "

root at giggles:~/bin# bash test.sh -z sdd
label: gpt
ptv[@] is "0fc63daf-8483-4772-8e79-3d69d8477de4 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f 21686148-6449-6e6f-744e-656564454649 c12a7328-f81f-11d2-ba4b-00a0c93ec93b 0fc63daf-8483-4772-8e79-3d69d8477de4 "
ftv[@] is "ext4 swap  vfat ext4 "

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: util-linux 2.34-0.1ubuntu9.1
ProcVersionSignature: Ubuntu 5.4.0-52.57-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.10
Architecture: amd64
CasperMD5CheckResult: skip
Date: Sat Oct 24 11:50:53 2020
InstallationDate: Installed on 2020-09-19 (35 days ago)
InstallationMedia: Xubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: util-linux
UpgradeStatus: No upgrade log present (probably fresh install)

** Affects: util-linux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug focal

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to util-linux in Ubuntu.
https://bugs.launchpad.net/bugs/1901343

Title:
  timing bug creates interacctions between util-linux utitlities

Status in util-linux package in Ubuntu:
  New

Bug description:
  This is a creepy bug that seems to disappear under examination.  In
  this case it appears that the bug is a timing bug, and introducing
  delays makes it go away.  I call this sort of thing a "frankenbug"
  because of creepyness and difficulty diagnosing.

  It appears to be an interaction between a call to sfdisk(8) and a
  subsequent call to lsblk(8).  I have a test script that displays the
  bug on my systems under the right circumstances -- in particular, on
  my core i-7 Dell 990, it shows up when reporting on a USB 3.0 GPT
  stick, but not when reporting on the boot drive /dev/sda formatted
  with MBR.

  This is a much simplified program, derived from a backup utility I've
  been working on.  You can run it with no delays (default) or introduce
  delays with the -z (sleep 1) switch or the -y (sync) switch.  The
  correct output occurs with the -z switch.  In the others, the
  partition types are not reported.  There should be no difference.

  Example runs:

  root at giggles:~/bin# bash test.sh sdd
  label: gpt
  ptv[@] is ""
  ftv[@] is "ext4 swap  vfat ext4 "

  root at giggles:~/bin# bash test.sh -z sdd
  label: gpt
  ptv[@] is "0fc63daf-8483-4772-8e79-3d69d8477de4 0657fd6d-a4ab-43c4-84e5-0933c84b4f4f 21686148-6449-6e6f-744e-656564454649 c12a7328-f81f-11d2-ba4b-00a0c93ec93b 0fc63daf-8483-4772-8e79-3d69d8477de4 "
  ftv[@] is "ext4 swap  vfat ext4 "

  ProblemType: Bug
  DistroRelease: Ubuntu 20.04
  Package: util-linux 2.34-0.1ubuntu9.1
  ProcVersionSignature: Ubuntu 5.4.0-52.57-generic 5.4.65
  Uname: Linux 5.4.0-52-generic x86_64
  ApportVersion: 2.20.11-0ubuntu27.10
  Architecture: amd64
  CasperMD5CheckResult: skip
  Date: Sat Oct 24 11:50:53 2020
  InstallationDate: Installed on 2020-09-19 (35 days ago)
  InstallationMedia: Xubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
  SourcePackage: util-linux
  UpgradeStatus: No upgrade log present (probably fresh install)

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1901343/+subscriptions