Re: RFC: patch to allow lock-free traversal of lists with insertion

From: Dipankar Sarma (
Date: Tue Oct 09 2001 - 02:46:26 EST

On Tue, Oct 09, 2001 at 12:43:55PM +0530, BALBIR SINGH wrote:
> 1) On Alpha this code does not improve performance since we end up using spinlocks
> for my_global_data anyway, I think you already know this.

It may if you don't update very often. It depends on your
read-to-write ratio.

> The approach is good, but what are the pratical uses of the approach. Like u mentioned a newly
> added element may not show up in the search, searches using this method may have to search again
> and there is no way of guaranty that an element that we are looking for will be found (especially
> if it is just being added to the list).
> The idea is tremendous for approaches where we do not care about elements being newly added.
> It should definitely be in the Linux kernel :-)

Either you see the element or you don't. If you want to avoid duplication,
you could do a locked search before inserting it.
Like I said before, lock-less lookups are useful for read-mostly
data. Yes, updates are costly, but if they happen rarely, you still benefit.


Dipankar Sarma  <> Project:
Linux Technology Center, IBM Software Lab, Bangalore, India.
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