Re: [boost] Re view Request: future library (N2561/Williams version)

From: Anthony Williams (anthony_w.geo_at_[hidden])
Date: 2008-05-12 08:17:50

"Peter Dimov" <pdimov_at_[hidden]> writes:

> Anthony Williams:
>
>> One way to do this is have the pool use packaged_tasks internally, and set 
>> a
>> wait callback which is invoked when a thread waits on a future from a pool
>> task. When the callback is invoked by the waiting thread (as part of the 
>> call
>> to wait()), if that waiting thread is a pool thread, it can proceed as
>> above.
>
> It actually doesn't matter whether the waiting thread is a pool thread or 
> not. If the task hasn't been scheduled, it can be "stolen" and executed 
> synchronously from within the wait(). 

Yes, you could do that. I'm not convinced it's necessarily a good idea,
though. Different threads potentially have different priorities or access
permissions. Also, thread interruption will behave differently: in my
prototype implementation, future::wait() is an interruption point. If a call
to wait() stole a task from a thread pool, interrupting the thread would
instead interrupt the task, which is not necessarily what was intended, as
this may have consequences for other threads waiting on that task.

Anthony
-- 
Anthony Williams            | Just Software Solutions Ltd
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