Re: [PATCH v3 0/4] kmod: help make deterministic

[Jessica Yu]

+++ Luis R. Rodriguez [27/06/17 00:44 +0200]:
> On Mon, Jun 26, 2017 at 11:37:36PM +0200, Jessica Yu wrote:
> > +++ Kees Cook [20/06/17 17:23 -0700]:
> > > On Tue, Jun 20, 2017 at 1:56 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxxx> wrote:
> > > > On Fri, May 26, 2017 at 02:12:24PM -0700, Luis R. Rodriguez wrote:
> > > > > This v3 nukes the proc sysctl interface in favor for just letting userspace
> > > > > just check kernel revision. Prior to whenever this is merged userspace should
> > > > > try to avoid hammering more than 50 kmod threads as they can fail and it'd
> > > > > get -ENOMEM.
> > > > >
> > > > > We do away with the old heuristics on assuming you could end up with
> > > > > less than max_threads/2 < 50 threads as Dmitry notes this would mean having
> > > > > a system with 16 MiB of RAM with modules enabled. It simplifies our patch
> > > > > "kmod: reduce atomic operations on kmod_concurrent" considerbly.
> > > > >
> > > > > Since the sysctl interface is gone, this no longer depends on any
> > > > > other patches, the series is independent. As usual the series is
> > > > > available on my linux-next 20170526-kmod-only branch which is based
> > > > > on next-20170526.
> > > > >
> > > > > [0] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=20170526-kmod-only
> > > > >
> > > > >   Luis
> > > > >
> > > > > Luis R. Rodriguez (4):
> > > > >   module: use list_for_each_entry_rcu() on find_module_all()
> > > > >   kmod: reduce atomic operations on kmod_concurrent and simplify
> > > > >   kmod: add test driver to stress test the module loader
> > > > >   kmod: throttle kmod thread limit
> > > >
> > > > About a month now with no further nitpicks. What tree should these changes
> > > > go through if there are no issues? Andrew's, Jessica's ?
> > >
> > > Seems like going through Jessica's would make the most sense?
> >
> > Would be happy to take patches 01 (which I need to anyway), 02,
> > possibly 04 if decoupled from the test driver (03).
>
> Feel free to decouple it, but note that then the commit log must then be
> changed. My own take is this fix is not so critical as it is a corner case, so
> I have instead preferred to couple in the test case and respective fix
> together. I'll leave it up to you how to proceed.

I'll take 01 and 02 for the next merge window, as they are
straightforward. 03/04 can stay together, and as I understand it 04
may need to switch back to using the normal wait_* api.

> > I can't take patch 03 through my tree just yet, as I haven't had time to give
> > it a look yet :-/
>
> Understood. I'd appreciate at least a review though.

Of course! I should have rephrased and said *by this upcoming merge window. 

> > [ Side comment, it seems that kmod.c isn't directly maintained by anyone
> > right now, perhaps Luis would be interested in picking it up? :-) ]
>
> Sure thing, I'm not sure if it makes sense to decouple kernel/kmod.c on
> MAINTAINERS though, if you do let me know what you'd prefer to call it,
> "KMOD MODULE USERMODE HELPER" ?
>
> If you prefer to keep them together I can certainly volunteer to review all
> kmod changes and can send a patch to add kmod and myself under "MODULE
> SUPPORT".

I'm not the maintainer for kmod.c, if that's what you mean by
decoupling. But I don't think it has one, which is why I'm suggesting
adding it to MAINTAINERS, since you've been actively working on it :)
(looking at git log, it looks like Andrew did most of the sign-off's
for kmod.c in the past). I think a separate entry in MAINTAINERS is
good, with the name you suggested.

Thanks!

Jessica