Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : Uenal Mutlu
Date : Sat May 21 2005 02:00 am

"Maciej Sobczak" wrote
> Uenal Mutlu wrote:
>
> >>How do you achieve the "wait for something to be done"?
> >>
> >>Example:
> >>One thread moves some elements from one container to another. I want to
> >>know (in different thread) when it is done.
> >
> > I personally do use an atomic flag
>
> But I mean - how do you *wait* for it to happen?
>
> If you use the flag, then how do you know *when* to check this flag?
> Do you wait? Or do you just check the flag "from time to time"?

It depends on the situation.
In a time-critical application I usually do the following:
  while (!fMyFlag)
     MyYield();    // gives up the rest of the time slice, ie. SwitchToOtherThread
  //...

in a non time critical situation I mostly do use something like that:
  while (!fMyFlag)
     MySleep(100);    // sleeps 100 ms
  //...

As said, in the examples above the variable fMyFlag is an atomic type, because
it is accessed by at least 2 threads.

But, most people do use WaitForSingleObject() and WaitForMultipleObjects() on Win32.

.