Subj : lock on IA-32
To   : comp.programming.threads
From : Michael Pryhodko
Date : Wed Mar 09 2005 04:56 pm

Is it possible to implement lock on IA-32 without using LOCK prefix
using following considerations:

a) there could be arbitrary number of threads trying to grab the lock
b) every thread has **unique** number P != 0 (this is main thing behind
this whole idea)

I was trying to build something like:

init:
A = 0
B = 0

LOCK:
@:
if (A == 0)
..   A = P
..   SFENCE
..   if (A == P && B == 0)
..       B = P
..       SFENCE
..       if (A == P && B == P)
..           // we've got the lock
..           // otherwise goto @:

obviosly example above does not work. I spent some time modifying it,
but every variant was discarded in time.

Could anyone give me an insight?

Also (since I do not now much about AMD architecture): is it possible
on AMD architecture?

Bye.
Sincerely yours, Michael.

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