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To: Linus Torvalds <torvalds@transmeta.com>
cc: linux-kernel@vger.kernel.org, lse-tech@sourceforge.net,
        Paul.McKenney@us.ibm.com, rusty@rustcorp.com.au
Subject: Re: [Lse-tech] Re: RFC: patch to allow lock-free traversal of lists with insertion
In-Reply-To: <Pine.LNX.4.33.0110131015410.8707-100000@penguin.transmeta.com>
From: Andi Kleen <ak@muc.de>
Date: 13 Oct 2001 20:42:34 +0200
In-Reply-To: Linus Torvalds's message of "Sat, 13 Oct 2001 10:23:23 -0700 (PDT)"
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In article <Pine.LNX.4.33.0110131015410.8707-100000@penguin.transmeta.com>,
Linus Torvalds <torvalds@transmeta.com> writes:

>  - nobody has shown a case where existing normal locking ends up being
>    really a huge problem, and where RCU clearly helps.

The poster child of such a case is module unloading. Keeping reference
counts for every even non sleeping use of a module is very painful. 
The current "fix" -- putting module count increases in all possible module 
callers to fix the unload races is slow and ugly and far too subtle to 
get everything right. Waiting quiescent periods before unloading is a nice 
alternative.

-Andi
-
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