Message-ID: <3BC3D9ED.6050901@wipro.com>
Date: Wed, 10 Oct 2001 10:47:33 +0530
From: "BALBIR SINGH" <balbir.singh@wipro.com>
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To: Linus Torvalds <torvalds@transmeta.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: [Lse-tech] Re: RFC: patch to allow lock-free traversal of lists with insertion
In-Reply-To: <OF296D0EDC.4D1AE07A-ON88256AE0.00568638@boulder.ibm.com> <20011010040502.A726@athlon.random> <9q0ku6$175$1@penguin.transmeta.com>
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Linus Torvalds wrote:

>In article <20011010040502.A726@athlon.random>,
>Andrea Arcangeli  <andrea@suse.de> wrote:
>
>>On Tue, Oct 09, 2001 at 08:45:15AM -0700, Paul McKenney wrote:
>>
>>>Please see the example above.  I do believe that my algorithms are
>>>reliably forcing proper read ordering using IPIs, just in an different
>>>way.  Please note that I have discussed this algorithm with Alpha
>>>architects, who believe that it is sound.
>>>
>>The IPI way is certainly safe.
>>
>
>Now, before people get all excited, what is this particular code
>actually _good_ for?
>
>Creating a lock-free list that allows insertion concurrently with lookup
>is _easy_.
>
>But what's the point? If you insert stuff, you eventually have to remove
>it. What goes up must come down. Insert-inane-quote-here.
>
>And THAT is the hard part. Doing lookup without locks ends up being
>pretty much worthless, because you need the locks for the removal
>anyway, at which point the whole thing looks pretty moot.
>
>Did I miss something?
>
>		Linus
>

What about cases like the pci device list or any other such list. Sometimes
you do not care if somebody added something, while you were looking through
the list as long as you do not get illegal addresses or data.
Wouldn't this be very useful there? Most of these lists come up
at system startup and change rearly, but we look through them often.

Me too, Did I miss something?

Balbir

>
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