[fpc-devel] volatile variables

Andrew Brunner andrew.t.brunner at gmail.com
Thu Jun 30 15:29:08 CEST 2011

On Thu, Jun 30, 2011 at 8:04 AM, Michael Schnell <mschnell at lumino.de> wrote:

> - if the potential cache incoherency would not be handled by Hardware / OS
> / Libraries on behalf of user land programs, I feel that this would so
> disastrous and ubiquitous that it result in so many programs not working on
> SMP systems that it would be a really well known issue.

I agree.  This problem when encountered was hidden during steady state
testing.  The list was consistently working as expected.  Where it
failed was when the core was ~80% usage and it walked - and it was on
my test system here using daily Ubuntu x64 builds - lord knows what
kernel it had those days.

Infact, it could possibly be an ubiquitous exploit waiting for
disaster when code normally running code encounters stale values
across cores.  You can imagine systems designed to never fail - fail
for no known reason at all...

In a case I observed, it did cause a significant problem to the
server.  Yes, it was disastrous, and ONLY evident during stress tests.

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