Subj : Re: Challenge: Multithreading & Synchronization
To   : comp.programming.threads
From : Uenal Mutlu
Date : Sat May 21 2005 03:53 am

"David Schwartz" wrote
>
> "Uenal Mutlu" wrote in message
>
> >> See also this DOC of Micro$oft:
> >> http://www.microsoft.com/whdc/driver/kernel/locks.mspx
> >> (http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfeae4b45/Locks.doc)
> >
> > Citation from the above DOC:
> >
> > "InterlockedXxx Routines
> > The InterlockedXxx routines perform common arithmetic and logical
> > operations atomically,
> > ensuring correct results on SMP systems. Whenever possible, drivers should
> > use these routines.
> > Most of them are native processor instructions and therefore do not
> > require a lock.
> > The InterlockedXxx routines can be used with pageable data. They are
> > usually
> > implemented inline by the compiler and can be called at any IRQL."
>
>     Then you've reinvented a less-efficient version of the spinlock.
> Congratulations.
> (Hint: What is the InterlockedXxx routine to check the value of a something without unsharing it?)

Wrong. All the effort is because it IS shared! If yo don't see it then I'm sorry for you:

thread1:
  sets the shared condition variable.

thread2:
  sets the shared condition variable.

thread3:
   waits for the shared condition variable to have a specific value.

Do you now understand that it is shared by multiple threads?
The variable could also be set to any other value but just the 0 and 1.

.