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Date: Mon, 22 Apr 2002 21:05:56 -0400 (EDT)
From: Alexander Viro <viro@math.psu.edu>
To: Matthew Dharm <mdharm-kernel@one-eyed-alien.net>
cc: Linus Torvalds <torvalds@transmeta.com>, Keith Owens <kaos@ocs.com.au>,
        linux-kernel@vger.kernel.org
Subject: Re: [RFC] race in request_module()
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On Mon, 22 Apr 2002, Matthew Dharm wrote:

> Isn't the real problem here that we've got a "rogue" running around
> removing things that we might be about to use?
> 
> Yes, I think that request_module() should indicate to the caller if
> something "suitable" was found.  But I think having rmmod -a running around
> sweeping things randomly is bad.
> 
> Perhaps what we need is a way to tell _how_long_ago_ the count on a module
> last changed.  Thus, rmmod -a could decide to only remove modules that were
> last used more than an hour ago, or somesuch.  Push the policy question into
> userspace.

Still doesn't solve the problem.  And BTW, there are userland races of
similar kind - foo.o depends on bar.o, modprobe loads bar.o, goes to look
for foo.o and gets bar.o removed from under it.

The thing being, relying on time doesn't help - e.g. we might have modules
on automounted volume and delays may be really long if the thing happens
at time when load is high.

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