[Bug 1781169] Re: frontend locking

[Łukasz Zemczak]

Hello Julian, or anyone else affected,

Accepted apt into bionic-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/apt/1.6.5 in a few
hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-bionic to verification-done-bionic. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-bionic. In either case, without details of
your testing we will not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: apt (Ubuntu Bionic)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-bionic

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https://bugs.launchpad.net/bugs/1781169

Title:
  frontend locking

Status in apt package in Ubuntu:
  Fix Released
Status in apt source package in Xenial:
  In Progress
Status in dpkg source package in Xenial:
  New
Status in apt source package in Bionic:
  Fix Committed
Status in dpkg source package in Bionic:
  New

Bug description:
  [Impact]
  apt acquires /var/lib/dpkg/lock but has to release it while running dpkg, offering a short window for other clients to acquire the lock. This implements /var/lib/dpkg/lock-frontend which will be acquired earlier and not released by apt for dpkg to run.

  dpkg will try to acquire the frontend lock as well, unless told not to
  do so via an environment variable, which apt does; hence concurrent
  runs of dpkg without other locking can't happen.

  [Test case]
  Run strace apt install $something and check that lock-frontend is acquired at the beginning and not released until the end.

  [Regression potential]
  Frontend locking failures are in English, as there are no translations yet. More locks also mean more potential for locking to go wrong across programs, but since we don't have any waiting locks we at least won't deadlock.

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