[cpp-threads] Thread try/time_join (was: Asynchronous FunctionProposal)

[Howard Hinnant]

On Jun 3, 2009, at 12:03 PM, Peter Dimov wrote:

> Howard Hinnant:
>
>> My concern is that not everyone needs try/timed join, but if we  
>> put  this functionality into the base level API, then everyone will  
>> pay for  it via higher overhead and lower performance.
>
> Proper joins do not really have a measurable performance cost. They  
> do impose a space overhead over a pthread_t (but not over a Windows  
> HANDLE.)
>
>> If we can't do it with a layout that looks like:
>>
>> class thread
>> {
>>    pthread_t id_;
>> public:
>>    ...
>> };
>>
>> then it doesn't belong in the lowest level API.
>
> We could've achieved the above. It is a rare case in which a  
> pthread_t is overencapsulated, as most kernel primitives on which  
> pthread_join is built do in fact offer the semantics we want. It is  
> a matter of surfacing it, and the POSIX WG has actually been willing  
> to consider extensions to the current join functionality.
>
> In N2178, I've written up my suggested extensions to pthreads upon  
> which we could build the "C++ pthreads".
>
> But I'm not, at this point, arguing in favor of N2178. This train  
> has long left the station.

I also note that boost::thread now supports timed_join, both relative  
and absolute variants. ;-)

Still, once Anthony put interrupt() into boost::thread, he pretty much  
doomed std::thread to DOA (and rightly so).

-Howard