Subj : Re: double-checked locking in C
To   : comp.programming.threads
From : David Schwartz
Date : Wed Jul 06 2005 11:56 pm


"Laurent Deniau" <Laurent.Deniau@cern.ch> wrote in message 
news:42CC493F.4020705@cern.ch...

> Now, there is the problem of reflecting the change of the side effects to 
> other threads. My suggestion was to put the flag inside the side object 
> itself. Therefore if the init_value is seen, the object is also seen. Of 
> course you may think that the object takes place on cache line boundary 
> and is only partially updated. That is in the worst case, only the flag 
> part and not the rest. But I am not sure if this can happen.

    You just don't get it. We're talking about *PORTABLE* code written for 
an abstract machine. There is no such thing as a cache line.

    You have the guarantees the standards give you. And that's it. If you 
claim anything else is guaranteed, then you have code that's *not* portable.

    You said:

>There is a simple, portable, processor independent, compiler independent 
>idiom which consists of delegating the work to an extern function, a 
>function with an implementation in a different translation unit.

    And then you went and talked about different types of caches! Portable 
processor independent compiled independent code cannot be dependent on what 
caches do.

    DS

.