[zeromq-dev] zmq::poll timeout returns immediately on MacOS/X 10.5

[Matt Weinstein]

On Jun 10, 2010, at 4:03 PM, Martin Sustrik wrote:

> Matt,
>
>> I inserted a zmq::poll into the client side of the sample client/ 
>> server
>> application --
>>
>> ...
>>
>>    zmq_pollitem_t pi;
>>    pi.socket = s;
>>    pi.fd = 0;
>>    pi.events = ZMQ_POLLIN;
>>    pi.revents = 0;
>>    assert(zmq::poll(&pi, 1, TIMEOUT) == 0);
>>
>>    // inserted before
>>    s.recv (&reply);
>>
>> ...
>>
>>
>> If TIMEOUT is set to -1 this waits for the response, any other value
>> returns immediately.
>>
>> Am I missing something?
>
> No. This is a generic issue. Documentation says that function waits  
> "up
> to" timeout interval, i.e. it can return prematurely.
Probably I'd change that to "may wait up to", with a big footnote :-)
>
> Exact waiting is possible, but it would have performance impact on
> zmq_poll. Others want to have poll as fast as possible, so it's hard
> decision to make.
>
> Thoughts anyone?

What would the kernel do? :)

One tack might be one condition variable per user thread, and a high- 
priority service thread running a wake-up queue (pointing at a list of  
unrolled lists...)?

> Martin
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