Should core.sync.mutex.Mutex, core.sync.condition.Condition, etc. have all their methods be shared?

[Dmitry Olshansky]

11/18/2012 11:13 AM, Alex Rønne Petersen пишет:
> On 18-11-2012 05:58, Jonathan M Davis wrote:
>> On Sunday, November 18, 2012 05:51:00 Alex Rønne Petersen wrote:
>>> On 18-11-2012 05:46, Jonathan M Davis wrote:
>>>> I don't know if we can answer this for sure at the moment given the
>>>> ongoing
>>>> discussion on shared, but looking at core.sync, it occurred to me that
>>>> there's a major problem with the classes in there. None of the work
>>>> with
>>>> shared. And unless I'm missing something here, I don't see how many of
>>>> them are even useful as anything other than shared. After all, what
>>>> good
>>>> is a mutex which is thread-local? But none of the methods on Mutex
>>>> or its
>>>> friends are shared.
>>>>
>>>> So, the question is should the all have their methods shared? And if
>>>> they
>>>> should, is there any reason to have non-shared overloads for them? What
>>>> good are they as anything other than shared? How is anyone using them
>>>> right now?
>>>>
>>>> - Jonathan M Davis
>>>
>>> Not at this point in time. It would break a ridiculous amount of code if
>>> we did this, given the current extremely annoying nature of shared.
>>>
>>> Most D code I have seen in the wild just shares mutexes, conditions, etc
>>> with __gshared or some other mechanism anyway, so I don't think there's
>>> anything to gain. Like, what would shared actually buy you here?
>>
>> __gshared is a good reason for leaving non-shared overloads, but isn't
>> code
>> really supposed to be using shared and not __gshared unless it's
>> specifically
>> extern(C)? That being the case, I'd expect shared to be the correct
>> thing to
>> use with mutexes normally, and right now, that won't work without a
>> ton of
>> casting or adding shared overloads.
>>
>> - Jonathan M Davis
>>
>
> I don't know what anything that has to do with shared is supposed or not
> supposed to do. It is not clear, even to the primary language designers,
> what shared actually is, so I really can't say anything to this...
>

Let's please stop this mantra. It buy us nothing but FUD.

One thing is clear - shared is not going away over night. Yes, having 
auto-magic atomic ops for various builtins is discussed, the kind of 
memory model is discussed.

Everything else stays. It's the globally shared data and it has tight 
restrictions on what you can do with it. As such it is (just like 
immutable) is safely passable between threads.

> All I can say is, let's wait with this until we know what shared is
> going to actually do. We don't want to do something we'll regret later.

Obviously we know what shared is. It's just certain details need 
straightening up. And certainly druntime/std.concurrency should add more 
support for it where meaningful.

-- 
Dmitry Olshansky