Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : David Schwartz
Date : Fri May 20 2005 04:58 pm


"Uenal Mutlu" <520001085531-0001@t-online.de> wrote in message 
news:d6lprf$70p$01$1@news.t-online.com...

> 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
>  //...

    And if there is no other thread?

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

    Hard to imagine a mutex in a non-time critical situation. Why 
deliberately write bad code?

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

    The use of an atomic type is insufficient. For platform-specific code, 
memory barriers or interlocked operations must be used. For portable code, 
mutexes must be used.

    Atomic operations are atomic with respect to a single processor only, 
that is, code cannot be interrupted or signalled during the operation. They 
have no special SMP or multi-threading semantics.

    DS

.