[cpp-threads] Interruption (was: Asynchronous FunctionProposal)

[Boehm, Hans]

> -----Original Message-----
> From:  Howard Hinnant
> 
> On Jun 3, 2009, at 6:06 PM, Boehm, Hans wrote:
> 
> interrupt & join, or at least interrupt & wait for 
> acknowledgement of interrupt would make excellent ~thread() 
> semantics in my opinion.  The only time ~thread() should have 
> any work to do is when it executes during exception-driven 
> stack unwinding.  However if there is no 
> interrupt-and-don't-wait, then the following code is going to 
> have extremely poor performance:
> 
> vector<thread> v;
> try
> {
>     ...
> }
> catch (std::ive_been_interrupted&)
> {
>     for (auto i = v.begin(); i != v.end(); ++i)
>          i->interrupt();                 // I don't want to wait here
>     for (auto i = v.begin(); i != v.end(); ++i)
>          i->join();                      // I want to wait 
> here instead
>     throw;                               // All v-threads should  
> interrupt in parallel, not sequentially
> }
> 
> If you put too many seat belts in the car, the driver won't 
> be able move enough to safely drive it.  There has to be a 
> reasonable compromise between safety and functionality.  
> Especially if we're threading for performance reasons.
Good point.  And if there's a chance of getting the car without all the extra seat belts, I agree.  But if all we can get is interrupt_and_join(), is that better than no car?  Is this less troubling to people than the other proposals?

(It still means that you need to use loops with timeouts or the like on I/O to make a thread interruptable.  But that seems far better than what we have now.)

Hans

> 
> -Howard
> 
> 
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