** Changed in: apt (Ubuntu Bionic)
Status: Triaged => In Progress
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https://bugs.launchpad.net/bugs/1778547
Title:
Broken system lock counting
Status in apt package in Ubuntu:
Fix Committed
Status in apt source package in Xenial:
Confirmed
Status in apt source package in Artful:
Confirmed
Status in apt source package in Bionic:
In Progress
Bug description:
[Impact]
System lock unrefing is broken, off-by-one error. Locking twice opens a
second fd for the lock file, and the old fd gets lost and remains open for the
remaining duration of the program
[Test case]
Executing the following script should show one lock file in the first
line, and none in the last line.
def maybe_readlink(path):
try:
return os.readlink("/proc/self/fd/" + p)
except:
return "<deleted>"
import os, apt_pkg
apt_pkg.init()
apt_pkg.pkgsystem_lock()
apt_pkg.pkgsystem_lock()
apt_pkg.pkgsystem_unlock()
apt_pkg.pkgsystem_unlock()
print([(p, maybe_readlink("/proc/self/fd/" + p)) for p in
os.listdir("/proc/self/fd")])
[Test output]
good, cosmic:
[('0', '/dev/pts/2'), ('1', '/dev/pts/2'), ('2', '/dev/pts/2'), ('3',
'/var/lib/dpkg/lock'), ('4', '<deleted>')]
[('0', '/dev/pts/2'), ('1', '/dev/pts/2'), ('2', '/dev/pts/2'), ('3',
'<deleted>')]
bad, bionic:
[('0', '/dev/pts/0'), ('1', '/dev/pts/0'), ('2', '/dev/pts/0'), ('3',
'pipe:[40889331]'), ('4', '/var/lib/dpkg/lock'), ('5', '/var/lib/dpkg/lock'),
('6', '<deleted>'), ('17', 'socket:[53931]')]
[('0', '/dev/pts/0'), ('1', '/dev/pts/0'), ('2', '/dev/pts/0'), ('3',
'pipe:[40889331]'), ('4', '/var/lib/dpkg/lock'), ('5', '<deleted>'), ('17',
'socket:[53931]')]
[Regression potential]
A locking change can potentially break locking, but this one seems like an
obvious off-by-one error.
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