Re: Concurrent access to packed arrays

[Florian Weimer <fw@deneb.enyo.de>]

Mats Weber <matsw@mac.com> writes:

> Yes, I think there are. When task B writes the data, it will do
> something like
> 
>    The_String(Last_Written + 1) := ...
>    Last_Written := Last_Written + 1;
> 
> on modern architectures, the memory accesses can get reordered, i.e.
> Last_Written can get updated before The_String and reading tasks will
> read uninitialized data.

Very good point.  Thanks.  (Not every architecture has complex cache
coherency protocols like Intel's. ;-)

So I'm going to add an interface which uses a protected type.
(There's no need to use it by default because most of the time, no
concurrent access occurs.)