Subj : Re: Lock-free buffer
To   : comp.programming.threads
From : Joe Seigh
Date : Fri Mar 04 2005 03:39 pm

On 4 Mar 2005 12:05:50 -0800, allan <hjcho@vt.edu> wrote:

> I am really curious if there exists the lock-free buffer algorithm.
> Lock-free queue, lock-free list, etc. are there, but is there the
> algorithm for the lock-free buffer?
>
> Lock-free queue is not sufficient for my case, because in the case
> where three readers try to read a data and the lock-free queue has
> only one data, only one of readers would get data with dequeue()
> operation and the other two should wait until writers fill data into
> the queue with enqueue() operation. In short, all readers should be
> guaranteed to get the latest updated data all the time.
>
> If anybody advices me, it would be deeply appreciated.
>

It sounds like you want a shared buffer.  A queue is a totally different
thing.

Yes, you can do it with COW (copy on write) which will allow lock-free
reads of the buffer.  atomic_ptr, RCU (Read, Copy, Update), SMR hazard
pointers, Boehm style GC, etc... will let you do that.  Updating the
buffer lock-free will require compare and swap or some other interlocked
primative.


-- 
Joe Seigh

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