Re: [RFC v2 3/6] kthread: warn on kill signal if not OOM

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Tejun,

On Sat, Sep 06, 2014 at 07:55:33AM +0900, Tejun Heo wrote:
> Hello, Dmitry.
> 
> On Fri, Sep 05, 2014 at 03:49:17PM -0700, Dmitry Torokhov wrote:
> > On Sat, Sep 06, 2014 at 07:31:39AM +0900, Tejun Heo wrote:
> > > On Sat, Sep 06, 2014 at 07:29:56AM +0900, Tejun Heo wrote:
> > > > It is for storage devices which always have guaranteed synchronous
> > > > probing on module load and well-defined probing order.
> > 
> > Agree about probing order (IIRC that is why we had to revert the
> > wholesale asynchronous probing a few years back) but totally disagree
> > about synchronous module loading.
> 
> I don't get it.  This is a behavior userland already depends on for
> boots.  What's there to agree or disagree?  This is just a fact that
> we can't do this w/o disturbing some userlands in a major way.

I am just expressing my disbelief that somebody relies on module loading
being synchronous with probing. Out of curiosity, do you have any
pointers?

> 
> > Anyway, I just posted a patch that I think preserves module loading
> > behavior and solves my issue with built-in modules. It does not help
> > Luis' issue though (but then I think the main problem is with systemd
> > being stupid there).
> 
> This sure can be worked around from userland side too by not imposing
> any timeout on module loading but that said for the same reasons that
> you've been arguing until now, I actually do think that it's kinda
> silly to make device probing synchronous to module loading at this
> time and age.  What we disagree on is not that we want to separate
> those waits.  It is about how to achieve it.

Well, there are separate things we want to solve. My main issue is not
with modules, but rather compiled-in drivers that stall kernel boot,
and these particular drivers are just fine if they are probed out of
bound.

> 
> > > To add a bit, if the argument here is that dependency on such behavior
> > > shouldn't exist and module loading and device probing should always be
> > > asynchronous, the right approach is implementing "synchronous_probing"
> > > flag not the other way around.  I actually wouldn't hate to see that
> > > change happening but whoever submits and routes such a change should
> > > be ready for a major shitstorm, I'm afraid.
> > 
> > I think we already had this storm and that is why here we have opt-in
> > behavior for the drivers.
> 
> It's a different shitstorm where we actively break bootings on some
> userlands.  Trust me.  That's gonna be a lot worse.

That did break bootings and that's why we reverted the wholesale async
probing.

Thanks.

-- 
Dmitry