Review Request: Replace thread usage with local event loop in kio/kio/hostinfo.cpp

[Albert Astals Cid]

On Dimarts 09 Agost 2011 14:57:06 David Faure wrote:
> > I just tried a test calling that function with 0 as timeout (so it always
> > timeouts) and sometimes it waits until 1 second so it is quite clear it
> > is waiting for the thread.
> 
> Yes, Thiago explained to me the notion of cancellation points, and proved
> me wrong. And since anyway terminate is a bad idea, this needs to be
> redesigned.
> 
> Thomas: I can't see how locking a mutex can work in a single-threaded case
> (there are no threads in your code; you seem to rely on the fact that Qt
> uses a thread internally in QHostInfo? That seems dangerous...).
> 
> Thiago and I came up with a design like this:
> * a single thread that makes async lookups. It's never blocked, it can
> always almost immediately read new requests from a queue and start them.
> * each request is encapsulated in a class that has the QString
> but also a QSemaphore.
> * the main thread can block using a timeout
> (QSemaphore::tryAcquire(timeout)) * the request class is stored using a
> shared pointer, so that it's only deleted when neither the main thread nor
> the worker thread need it anymore [otherwise the deletion is a problem, in
> the timeout case vs the normal case]

Works for me, do you need help implementing it [workwise not knowledgewise 
;)]?

Albert