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Re: Getting rid of circular dependencies, stage 3



On Tue, Jan 10, 2006 at 01:17:38AM +0200, Lars Wirzenius wrote:
> One things, if I've understood things correctly, is that it is not
> possible to reliably know how they're going to be removed -- dpkg will
> break the circle in a random place and this may or may not result in

the problems occur when apt processes "long" lists of packages, and more
specifically in the 'configure' stage.
dpkg has only partly to do with this; the problem is in APT and the way it
controls dpkg: due to a limited command line length, apt can only call dpkg
with a certain number of packages on the same time.
dpkg can handle circular dependencies fine as long as both 'ends' are fed in
at the same time.
but, at least the last time I checked the apt source, apt doesn't check 
for this condition when splitting the to-be-configured list and passing these
chunks to dpkg.
the last hack made by the apt people was to increase the length of these
chunks (which decreases the probability of the bugs invokation).

well, now people may say: "who ever feeds so many packages into apt at the same
time?" - answer: try an 'apt-get dist-upgrade' from woody to sarge...

> I don't know if that is sufficient reason to get rid of circular
> dependencies.
well, everything that makes package management tasks _interactive_ is a major
showstopper for use in bigger installations (hpc clusters, "enterprise" desktops).


ok. 'nuff ranted. 

-- 
c u
henning

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