Re: [boost] [threadpool] draft n2276 - interrupting tasks

Subject: Re: [boost] [threadpool] draft n2276 - interrupting tasks
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2008-11-24 04:47:47

k-oli_at_[hidden] writes:

> the draft specifies that the threapool::submit() function returns a future 
> object in order to retrieve the result of the submited task.
>
> What about task cancelation/interruption?

In the absence of thread interruption, task interruption is tricky.

> Instead returning a future the pool could return a task< R > object which 
> contains a future< R > (access over R task< R >::get()) and interruption 
> routines.

You could just add the interruption routines to unique_future.

> Following Herb Sutters sugestions the  submited task must be cooperative 
> (contain interruption_point).

Yes.

> What do you think? Should/Could it be added to the draft?

I think interruption support would be good for thread pools. Adding it
to the proposal requires careful thought due to the controversial
nature of thread interruption. One possibility I thought of was
passing in a cancellation callback with the task. If someone tries to
cancel the task, then it invokes the callback. This allows a user to
write their own cancellation tests (e.g. set an atomic flag). The
downside is you don't get the automatic cancellation points.

Anthony
-- 
Anthony Williams
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