[Bug 1831981] Re: aptdaemon frontend locking, locking fixes

[Brian Murray]

Hello Julian, or anyone else affected,

Accepted aptdaemon into disco-proposed. The package will build now and
be available at
https://launchpad.net/ubuntu/+source/aptdaemon/1.1.1+bzr982-0ubuntu21.1
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-disco to verification-done-disco. If it does not fix
the bug for you, please add a comment stating that, and change the tag
to verification-failed-disco. 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: aptdaemon (Ubuntu Disco)
       Status: Triaged => Fix Committed

** Tags added: verification-needed verification-needed-disco

** Changed in: aptdaemon (Ubuntu Cosmic)
       Status: Triaged => Fix Committed

** Tags added: verification-needed-cosmic

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https://bugs.launchpad.net/bugs/1831981

Title:
  aptdaemon frontend locking, locking fixes

Status in aptdaemon package in Ubuntu:
  Fix Released
Status in aptdaemon source package in Xenial:
  Triaged
Status in aptdaemon source package in Bionic:
  Fix Committed
Status in aptdaemon source package in Cosmic:
  Fix Committed
Status in aptdaemon source package in Disco:
  Fix Committed
Status in aptdaemon source package in Eoan:
  Fix Released

Bug description:
  [Impact]
  aptdaemon needs to implement frontend locking to avoid it hijacking dpkg status lock from clients that do implement frontend locking; and in order to be protected from apt clients that acquire the status lock (which they won't do if aptdaemon holds the frontend lock).

  This also change the locking order to lock in APT order, and the
  unlock order becomes the reverse of that so that the behavior is sane
  wrt other clients, as it was somewhat broken.

  [Test case]
  Lock /var/lib/dpkg/lock-frontend and then try do so something with aptdaemon, it should not be possible until you release lock-frontend.

  [Regression potential]
  There may be other race conditions appearing now due to the order of (un)locking changing.

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