[fpc-devel] LockFree Queue algorithm

Martin Friebe fpc at mfriebe.de
Sun Jan 27 15:11:36 CET 2008

What about a long running (eg daemon) application?

If temp/tail hits the upper boundary of Integer?

(If I understand it correctly)
I don't know if interlockedIncrement gives a boundary error, but if not,
it still fails.
- With currently integer, it gets a negative value, once crossing
0x7fffffff, and SetObject will attempt to read/write out-of-bounds memory.
- Assuming temp/tail being unsigned: it will go from 0xffffffff to 0.
"0xffffffff mod fsize" may return a value greater 0, "0x00 mod fsize"
will be zero. You make an unexpected jump within the list.


DarekM wrote:
> Hi
> This is my proposition of algorithm and its implementing multithreaded 
> FIFO queue without lock.
> First use array of pointers to handle messages.
> I've use it in my program, it works.
> I think it may by useful.
> site: http://www.emadar.com/fpc/lockfree.htm
> source: http://www.emadar.com/fpc/flqueue.pas
> There is also generic implementation of the same algorithm. Its my 
> first generic approach.
> Any help appreciated.
> it;s not so much text, but  source is very short, its explain much 
> better.
> Darek
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