Re: [boost] [asio] Question regarding io_service.post() and pool of threads

Subject: Re: [boost] [asio] Question regarding io_service.post() and pool of threads
From: Romain CHANU (romainchanu_at_[hidden])
Date: 2010-09-28 04:24:04

Hi Vivek,

I did a simple program that creates a pool of threads running
io_service.run() and calling a function many times (through
io_service.post() ) (like the simple program in the website given earlier).

My function accesses / modifies an object (without lock) and the program
just crashes.

I am not really sure of the behavior of functions posted to io_service (i.e
io_service.post() ) with multiple threads running io_service.run().

Anyone?

On 28 September 2010 14:21, Vivek Prakash <vivek.cs.iitr_at_[hidden]> wrote:

> Since shared objects are safe( except when calling reset() prematurely), I
> believe that there is no need to use a lock/semaphore.
>
> ~
> Vivek Prakash
>
>
> On Tue, Sep 28, 2010 at 8:48 AM, Romain CHANU <romainchanu_at_[hidden]>
> wrote:
>
> > Hi,
> >
> > I was looking at this website where the guy gives an interesting example
> > about the use of a pool of threads and io_service.post():
> >
> >
> >
> http://mostlycoding.blogspot.com/2009/05/asio-library-has-been-immensely-helpful.html
> >
> > However, something confuses me a bit, cf. the website "In just a bunch of
> > lines of code we have a thread pool executing any arbitrary task whenever
> > one thread is available. No need to address the usual multi-threading
> > issues
> > with concurrent jobs sharing few resources: just post what you need and
> let
> > io_service take care of it!"
> >
> > Extracted from Boost Asio reference: "The
> > io_service<
> >
> http://www.boost.org/doc/libs/1_44_0/doc/html/boost_asio/reference/io_service.html
> > >
> > guarantees
> > that the handler will only be called in a thread in which the run(),
> > run_one
> > (), poll() or poll_one() member functions is currently being invoked."
> >
> > For my understanding, since there is a pool of threads, a handler can run
> > concurrently in different threads, even though we are using
> > io_service.post().
> >
> > Is that correct? My concern here is about the need or not to lock the
> data
> > accessed by the handler.
> >
> > Thank you.
> >
> > Regards,
> >
> > Romain
> > _______________________________________________
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