Re: [9fans] OT: cannonical set of queue ops

["Richard Bilson" <rcbilson@gmail.com>]

On 12/6/06, LiteStar numnums <litestar@gmail.com> wrote:
> >For instance, if IsQueueEmpty returns "true", that answer isn't worth
> very much if, by
> > the time you act on that information, some other thread could have
> > added an item to the queue.
>
> Wouldn't it be natural for such a function to block the active thread
> until the desired
> result is achieved? Since this clean up thread wouldn't really need to
> be on a hard deadline, wouldn't WaitQueueEmpty make more sense then a
> IsQueueEmpty? The writer may be more difficult, but again, if the
> Queue is full, it must wait anyway, so blocking here wouldn't be too
> problematic, methinks.

You could do that as well, but that doesn't address the fundamental
problem that I was pointing out regarding IsQueueEmpty: once you wake
up you don't really know anything about the state of the queue, unless
you are sure that no other thread could be adding items. All you know
in general is that the queue was recently empty.

I agree with you that it's usually better to block than to busy-wait.