[Lazarus] thread safe

[Andrew Brunner]

On Mon, Jun 27, 2011 at 7:57 AM, Michael Schnell <mschnell at lumino.de> wrote:
> There is no question that we all agree about the technical background of all
> this.

Actually,

There was no mention of memory barriers other than the content in my
post.  So if you want to understand what that is here is a link...

http://en.wikipedia.org/wiki/Memory_barrier

Simply protecting a loop with a futex is not sufficient.  Assigning
variables in a multi-threaded environment is not sufficient.

Interlocked/Exchange/ExchangeAdd/Increment features must be used
whenever dealing with variables (with at least one exception)  In my
experience arrays of boolean are atomic.

I ran tests on a HexCore AMD system which had unexplained anomalies
with pointers in an bidirectional linked list.  I replaced all the
pointer assignments with InterlockedExchange and the system worked
flawlessly.  Some of the assignments were taking place in a
criticalsection (btw).