Comment 6 for bug 1829860

So disco, 1.8.3:

at the start:
openat(AT_FDCWD, "/var/lib/dpkg/lock-frontend", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 4
fcntl(4, F_SETFD, FD_CLOEXEC) = 0
fcntl(4, F_SETLK, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
openat(AT_FDCWD, "/var/lib/dpkg/lock", O_RDWR|O_CREAT|O_NOFOLLOW, 0640) = 5
fcntl(5, F_SETFD, FD_CLOEXEC) = 0
fcntl(5, F_SETLK, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0

end of run:

close(5) = 0
close(4) = 0
close(3) = 0

=> we unlock in reverse as we want.