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POKeeping two cross-communicating asio io_service objects busy
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copied!<p>I am using boost:asio with multiple io_services to keep different forms of blocking I/O separate. E.g. I have one io_service for blocking file I/O, and another for long-running CPU-bound tasks (and this could be extended to a third for blocking network I/O, etc.) Generally speaking I want to ensure that one form of blocking I/O cannot starve the others.</p> <p>The problem I am having is that since tasks running in one io_service can post events to other io_service (e.g. a CPU-bound task may need to start a file I/O operation, or a completed file I/O operation may invoke a CPU-bound callback), I don't know how to keep both io_services running until they are both out of events.</p> <p>Normally with a single I/O service, you do something like:</p> <pre><code> shared_ptr<asio::io_service> io_service (new asio::io_service); shared_ptr<asio::io_service::work> work ( new asio::io_service::work(*io_service)); // Create worker thread(s) that call io_service->run() io_service->post(/* some event */); work.reset(); // Join worker thread(s) </code></pre> <p>However if I simply do this for both io_services, the one into which I did not post an initial event finishes immediately. And even if I post initial events to both, if the initial event on io_service B finishes before the task on io_service A posts a new event to B, io_service B will finish prematurely.</p> <p>How can I keep io_service B running while io_service A is still processing events (because one of the queued events in service A might post a new event to B), and vice-versa, while still ensuring that both io_services exit their run() methods if they are ever both out of events at the same time?</p>

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