Revamped concurrency API (Don can you contact Bartosz ?)

[Don]

Nick B wrote:
> Nick B wrote:
>> Bartosz Milewski wrote:
>>> Nick B Wrote:
>>>>> Could you give us _any_ kind of test case (even if it's enormous)?
>>>> Bartosz - are you able to provide a test case as requested by Don ?
>>>> Then it might be possible, to get this bug fixed.
>>>>
>>>> Nick B.
>>>
>>> I can send you the files I have checked out.
>>> The problem was in core.thread. I tried to implement a struct Tid 
>>> (thread ID) with reference-counting semantics and deterministic 
>>> destruction. It passed all the tests, but when it was used in one 
>>> particular place in druntime it produced incorrect assembly. Even the 
>>> slightest change made the bug disappear, so I wasn't able to 
>>> reproduce it under controlled conditions.
>>>
>>> Unfortunately, I have undone some of my changes trying to bypass the 
>>> bug, so at the moment I don't even have the buggy version, but it can 
>>> be reconstructed. We can discuss it off-line, if you want. Use my 
>>> email address with -nospam removed.
>>
>> Bartosz
>>
>> I think that Don is the best person to contact you. I will try to 
>> contact him.
>>
>> Nick B
> 
> Don, are you able to contact Bartosz, re the details of this test case.
> 
> Nick B

Bartosz has sent it to me. I can reproduce the error. It's my top 
priority, but it'll take a while -- it's nasty.