Re: [gentoo-portage-dev] idea: strict run-time dependencies to remove perl-cleaner, python-updater...

[Finn Thain <fthain@telegraphics.com.au>]

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On Thu, 22 Sep 2005, pclouds wrote:

> Well, my aim is mainly perl, python, nautilus, gtk+ modules... As for 
> kernel modules, i'd rather all gentoo-provided kernel modules are 
> updated properly without exaustive search (too slow).

I don't think it would be slow. I say that because it only takes the 
kernel an instant to fail insmod on a incorrectly versioned module, on a 
slow machine (25 MHz). However, it would be slow to rebuild more modules 
than necessary.

Preventing that requires a heuristic that says, "module foo compiled 
against baz-x will not work with new baz-y, where y > x+n". This n is 
often an unknown when a module is emerged, so these rule can't be stated 
in the module ebuild. They have to be stated in the rebuilder that 
ships with baz-y. But preparing those rules would make it more difficult 
to prepare each new kernel release.

I agree that portage could make rebuilders rather easy to write for those 
things where you have a simple rule like "modules built against dep 
version 2.x work with any dep version 2.y". But Linux kernel versioning 
doesn't produce simple rules, and exhaustive searches don't need them.

-f

> People who manually install kernel modules should take care of 
> themselves :)
>
> On 9/22/05, Finn Thain <fthain@telegraphics.com.au> wrote:
> >
> > On Wed, 21 Sep 2005, pclouds wrote:
> >
> > > This is an idea.
> > > Everytime you update python, perl to a major version, you have to run
> > > perl-cleaner/python-updater to re-emerge all packages that depend on
> > > previous version. The situation is probably similar to kernel
> > > packages. When you re-compile and install new kernel, you need to
> > > re-emerge kernel packages to make sure it work properly. I'd rather a
> > > consistent approach to solve these problems instead seperate updater
> > > for separate programs such as python-updater, perl-cleaner.
> > >
> > > The idea is to use a number to identify compatibility. Those versions
> > > which have the same number are expected to work well with other
> > > installed programs. If the number is different, then all other depend
> > > programs should be re-emerged.
> >
> > I assume there is no such thing as a kernel-updater (at least there isn't
> > one on my system). Your suggestion would make it easier to write one. But,
> > since kernel symbol versioning is precise enough to detect ABI
> > compatibility between versions, isn't the problem largely solved in the
> > kernel? I'm not sure that such a script is needed other than to save you
> > from having to figure out what pkg contains the module that just broke?
> >
> > There is also the problem that some portion of gentoo users roll their own
> > kernels, without telling portage.
> >
> > So, if you wanted to write a kernel-updater, wouldn't it be better to
> > exhaustively check the module symbols against the Module.symvers file?
> > (There is also the vermagic field in modinfo, not sure where that comes
> > from. I'm assuming CONFIG_MODVERSIONS, but those not using that hopefully
> > know what they are doing anyway :-).
> >
> > >  When portage merge a package (A) to system, it allow the package to
> > > specify a number (or string, whatever) to specify a compatibility
> > > number. When other packages (e.g B) that depend on package A are
> > > merged, it will keep A's special number in /var/db/pkg. If package A
> > > is re-emerged and break compatibility, this number should change.
> > > Otherwise, this number remains the same.
> > > Those program like perl-cleaner, python-updater may benefit from these
> > > numbers. It may check for numbers stored in /var/db/pkg's B and number
> > > in A's. If these numbers differ, B should be re-emerged.
> > > As for python, all python 2.4's number should be "2.4" and python
> > > 2.2.x  should be "2.2". Perl is similar. As for kernel, the number
> > > should be timestamp.
> >
> > The rebuilder/module ebuilds don't need to know that version x is
> > compatible with version x+n if the rebuilder is only ever run upon ebuild
> > advise after an upgrade.
> >
> > Consequently, you could just have portage record the actual versions of
> > the deps that were in use at the time a pkg was emerged (if it doesn't
> > already?). Then the rebuilder just has to look for any kernel modules that
> > were emerged while depending on a kernel older than the present one. (I
> > don't know if this would help with package.provided kernels and
> > !CONFIG_MODVERSIONS kernels, it might.)
> >
> > IMHO an exhaustive search is still the best approach.
> >
> > (But don't ask me what you do if the module is not slotted and the
> > original kernel is still installed as a fall back...)
> >
> > -f
> >
> > > Suppose i can feed a kernel ebuild with a config file :), then everytime
> > > i change config, re-emege kernel, compatibility number should change.
> > > That's the signature for, say, kernel-updater to update all kernel
> > > packages.
> > >
> > > To implement this feature, ebuild should provide a function, say,
> > > pkg_version() that return compatibility number. Portage should store
> > > this number in /var/db/pkg. Also, when emerge an ebuild, portage
> > > should store current compatibility numbers of all direct dependencies.
> > > The rest of work is left to perl-cleaner, python-updater,
> > > kernel-updater ..., checking compatibility numbers and update packages
> > > appropriately.
> > >
> > > How about this?
> > > --
> > > Bi Cờ Lao
> > >
> > >
> >
> 
> 
> --
> Bi Cờ Lao
> 
>