** Description changed: - Frontend lock support for apt and dpkg is tracked in LP: #1781169, this - bug tracks unattended-upgrades changes + [Impact] + + Apt and dpkg implemented the Frontend Locking API and unattended- + upgrades needs to adopt it to not leave the packaging system unlocked + while passing control to python-apt and dpkg to perform package + installations and removals. Leaving the packaging system unlocked caused + many crashes of u-u when other tools took the lock and in the worse case + let other package management tools operate on dpkg's database breaking + systems. + + The change takes advantage of python-apt's new API and keeps the + frontend lock during the run of u-u and unlocks only the inner locks for + committing changes. + + [Test case] + + Run strace unattended-upgrades to upgrade several packages and check + that lock-frontend is acquired at the beginning and not released until + the end (not reacquired repeatedly). + + Unfixed u-u's output is like this: + # strace unattended-upgrade --verbose --dry-run 2>&1 | grep lock + openat(AT_FDCWD, "/var/run/unattended-upgrades.lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4 + openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6 + openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6 + openat(AT_FDCWD, "/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 93 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6 + openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6 + openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 6 + ... + + Fixed u-u's output is like that: + # strace unattended-upgrade --dry-run --verbose 2>&1 | grep lock + openat(AT_FDCWD, "/var/run/unattended-upgrades.lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4 + openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 8 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 10 + openat(AT_FDCWD, "/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 57 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 10 + openat(AT_FDCWD, "/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 69 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 10 + openat(AT_FDCWD, "/var/cache/apt/archives/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 70 + openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 10 + ... + + [Regression potential] + + Incorrect lock API usage can make unattended-upgrades to crash, but it + is unlikely to hang since the lock handling operations are non-blocking. + Failing to reserve the locks can also cause problems by allowing other + package management tools to install packages in parallel, but this + problem existed in the past, too. + + [Additional Info] + Frontend lock support for apt and dpkg is tracked in LP: #1781169, this bug tracks unattended-upgrades changes
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1789637 Title: Proper support for frontend lock To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unattended-upgrades/+bug/1789637/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
