Static problem

[Stanislav Blinov]

Bob Cowdery wrote:
>  On 07/10/2010 21:32, Stanislav Blinov wrote:
>> Steven Schveighoffer wrote:
>>
>>>> What I'd propose is either:
>>>> 1) Create your own lock-free associative array (yup, reinvent the
>>>> wheel to introduce AA to the world of 'shared')
>>>> 2) In this small case it may seem best (though mind that often such
>>>> cases do grow up to the point when you still need to rethink design):
>>>> Make your associative array __gshared and perform synchronization by
>>>> hand, i.e. create a static Mutex (from core.sync.mutex) variable and
>>>> initialize it in your CRegistry's static ctor, and then enclose all
>>>> access to associative array in synchronized(mutex) {} blocks.
>>>>
>>>> Maybe concurrent-programming-in-D guru may propose simpler solution,
>>>> but I don't see another.
>>> FWIW, the classinfo of a class is an object, and as such can be used
>>> as sort of a global lock without having to use a static constructor:
>>>
>>> synchronized(this.classinfo)
>>> {
>>>    ....
>>> }
>>>
>>> -Steve
>> Thanks. To my shame, I repeatedly keep forgetting about this.
> Thanks for the suggestions. I'm keen to avoid locks as everything so far
> is message parsing and the system is real-time. Having lots of threads
> that all talk to each other I needed a place to keep the Tid's which is
> accessible to everyone. There is no conflict because the main thread
> creates all others and registers the Tid's. Once the threads go the
> registry is read only. Just setting __gshared makes the app work. This
> may not be good practice I know and I will come back to it when I have
> more time.
> 
> I'm not sure how to use synchronized(this.classinfo). Is this in
> combination with __gshared to synchronise access at the method level. Is
> it like a wrapper that goes inside the method?
> 
> bob

Yeah, it's like this:

static void register(E_PROC name, Tid tid)
{
	synchronized(this.classinfo)
	{
		theRegistry[name] = tid;
	}
}

static Tid getTid(E_PROC name)
{
	Tid* result;
	synchronized(this.classinfo)
	{
		result = name in TidRegistry;
	}
	//...
}

All Objects contain a 'monitor' which is a synchronization primitive.

synchronized(some_object)
{
	foo();
}

is similar to

{
	some_mutex.lock();
	scope(exit) some_mutex.unlock();
	// some code
}