harmony-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Rodrigo Kumpera <kump...@gmail.com>
Subject Re: Changes to bootjvm 0.0.0 coming soon
Date Tue, 18 Oct 2005 15:18:52 GMT
On 10/18/05, Archie Cobbs <archie@dellroad.org> wrote:
> Rodrigo Kumpera wrote:
> > This won´t help to find the spots that require memory barriers, as
> > these are only an issue on SMP systems. But your idea should not be
> > discarded as it may help with other kinds of problems.
>
> Good point.. interesting question how you could check that too..
> perhaps for multi-CPU systems you'd want to insert random length
> delay loops (instead of context switches) or something. A context
> swith would probably result in indirect flushing of the CPU state
> anwyay, effectively the same as a barrier between every instruction.
>
> -Archie
>
> __________________________________________________________________________
> Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com
>
>


Well, I think this kind of test requires that the thread observing
mutation be busy-waiting for changes and the test must be repeated a
huge ammout of times. For example, the new JMM says that changes to
volatile variables must be visible in the same order as they happen,
so:

volatile int a = 0, b = 0;

//Thread 1 repeats the following:
a = 0;
b = 0;
a = 1;
b = 2;

//Thread 2 must never see b = 2 and a = 0, so it repeats the following:
int ra = a;
int rb = b;
if(a == 0 && b == 2) //signal error

Given it's a SMP machine, both threads will be running concurrently.

Mime
View raw message