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Date: Tue, 8 Jan 2008 19:22:07 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Matt Helsley <matthltc@us.ibm.com>
Cc: Jan Beulich <jbeulich@novell.com>, hch@infradead.org, pagg@oss.sgi.com,
       erikj@sgi.com, pj@sgi.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] add task handling notifier
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On Tue, 08 Jan 2008 18:47:00 -0800 Matt Helsley <matthltc@us.ibm.com> wrote:

> > > 
> ...
> > > Am I to conclude then that there's no point in addressing the issues other
> > > people pointed out? While I (obviously, since I submitted the patch disagree),
> > > I'm not certain how others feel. My main point for disagreement here is (I'm
> > > sorry to repeat this) that as long as certain code isn't allowed into the kernel
> > > I think it is not unreasonable to at least expect the kernel to provide some
> > > fundamental infrastructure that can be used for those (supposedly
> > > unacceptable) bits. All I did here was utilizing the base infrastructure I want
> > > added to clean up code that appeared pretty ad-hoc.
> > > 
> > 
> > Ah.  That's a brand new requirement.
> 
> In all fairness it's not really a brand new requirement -- just one that
> wasn't strongly emphasized during prior attempts to get something like
> this in.
> 
> I had a mostly-working patch for this on top of the Task Watchers v2
> patch set. I never posted that specific patch because it had a race with
> module unloading and the fix only increased the overhead you were
> unhappy with. I mentioned it briefly in my lengthy [PATCH 0/X]
> description for Task Watchers v2 (http://lwn.net/Articles/207873/):
> 
> "TODO:
> ...
> I'm working on three more patches that add support for creating a task
> watcher from within a module using an ELF section. They haven't recieved
> as much attention since I've been focusing on measuring the performance
> impact of these patches."
> 
> <snip>
> 
> Would tainting the kernel upon registration of out-of-tree "notifiers"
> be more acceptable?

How does that work?  module.c does the register/deregister on behalf of the
module?

I certainly encourage people to disagreee with me here, but my current
thinking is:

- the cleanup aspect isn't worth the runtime overhead and

- the support-modular-users aspect is largely new and would need a lot
  more description and justification (with examples) before we can even
  begin to evaluate it.

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