[Mono-dev] ObjectPool

[Jérémie Laval]

There were indeed two bugs in there, a missing barrier and the issue you
described.

I also commented out the code if you want more details.

--
Jérémie Laval
http://neteril.org



On Wed, Jul 25, 2012 at 11:54 AM, Greg Young <gregoryyoung1 at gmail.com>wrote:

> We have had some moving forward in our mono stability issues. I
> figured I would start up a chat here about one place that seems to be
> causing many problems.
>
>
>
> https://github.com/mono/mono/blob/master/mcs/class/corlib/System.Collections.Concurrent/ObjectPool.cs
>
> I am not really sure the code here is actually thread safe... Maybe it
> doesn't need to be for some reason?
>
> We have added volatiles for add/remove index (yuriy pointed out that
> threads were often stuck at line 86) but even with that im still not
> sure its actually threadsafe. There are some weird edge conditions
> that seem to be here (like if CompareExchange fails 3 times it will
> just never set the remove index and continue on).
>
> Somebody has obviously spent a lot of time thinking about this code
> and optimizing it. I want to make sure we get the full "why" behind
> things so we dont a) waste time b) introduce issues.
>
> Greg
>
> --
> Le doute n'est pas une condition agréable, mais la certitude est absurde.
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