Subj : Re: a thread question
To   : comp.programming.threads
From : Uenal Mutlu
Date : Thu May 12 2005 02:01 am

"QQ" <junciu@yahoo.com> wrote
> Hi I am writing a multithreads program.
> I have a variable in the main thread,
> can I use it at the child thread?
> For example I have a count in main,
> when the count reaches 10, I will execute some command at the child
> is it OK?

Depends on the CPU, but normally if you define the shared integer
variable as "volatile" and place it at a CPU word boundary adress
then r/w operations will usually be done atomically by the CPU.
This is the fastest method, but it depends on the CPU + compiler,
though most do it this way.
A better and portable method would be to use an atomic counter.
A more universal method would be to use a locking mechanism
(which usually is based on atomic operations in its inners), for example
mutex, criticalsection, or a read-write-lock.

.