[dmd-concurrency] shared arrays

[Kevin Bealer]

I'd suggest setting the high bit of the length instead.  If I have this
scenario:

char[] foo = "abcd".dup;
char[] bar = foo[1..2];
Then bar is an array with an odd address.

Kevin
On Thu, Jan 14, 2010 at 10:16 AM, Sean Kelly <sean at invisibleduck.org> wrote:

> On Jan 14, 2010, at 4:10 AM, Steve Schveighoffer wrote:
>
> > Having implemented the array append patch to fix stomping, and reading
> the dmd-concurrency debate, I realized that what I implemented is no good
> for shared arrays.
> >
> > In fact, I wonder how shared arrays can support any array operations
>
> I sent an email about this a while back.  In short, if we're going to allow
> array ops on shared arrays at all I think they'll have to use atomic ops to
> "lock" the array for the length of the update.  Basically, set the 1 bit of
> the ptr field to indicate the array is locked.  This gets tricky when more
> than one shared array is involved because the lock has to be acquired on
> each, and because different ops may try to lock arrays in different orders,
> if a spinlock acquire times out the code will have to release all the locks
> it's acquired, wait some random interval, and try again.  Pretty complicated
> stuff if the goal is just to support shared array ops.
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