Re: [Boost-users] [asio] serial_port question

Subject: Re: [Boost-users] [asio] serial_port question
From: Robert Dailey (rcdailey_at_[hidden])
Date: 2009-08-26 12:32:12

On Wed, Aug 26, 2009 at 11:16 AM, Michael Caisse <
boost_at_[hidden]> wrote:

> Robert Dailey wrote:
>
>>
>> Would you recommend calling read_start() from its own thread and have it
>> loop indefinitely? I believe this is what you originally suggested. However,
>> I am curious about the issues with calling read_some() and write_some() from
>> separate threads without using any external synchronization techniques (i.e.
>> mutexes). Do I have to synchronize these two calls manually or is it done
>> internally? I'll re-review the documentation, but I did not see anything
>> regarding this earlier.
>>
>> Thanks for your help.
>>
>
> The io_service takes care of the "threading" issues for you. Just
> call read_start once from (lets say) main to get the processes going
> and then it all happens in the background... asynchronously. The
> call to read_start doesn't block. If you want different threads
> to operate on the io (though I recommend not doing this at first)
> then you can use a thread pool to call the io_service.run method
> from multiple threads.
>
> Have a look at some of the examples to see how it is all put
> together. Reading/writing to serial ports is the same as reading/writing
> to sockets using asio. I like to recommend the chat server/client
> example. It pulls together a lot of asio concepts in an easy to
> understand application.

Thanks, I'll have a look at that. I understand what you are saying. I
actually figured that out shortly after I posted. So I'm calling
read_start() at the beginning and letting it take over, however I have one
concern. I have a thread that loops, continuously calling io_service::run().
Will run() block while waiting for data to read? If so, this could
potentially block any writes that occur after it. For example, suppose I do
an async_read_some(), and then shortly after that I call
boost::asio::async_write(). Will the write be blocked by the read? I'm
probably going to be sending a lot more data than receiving it, and if this
is the case it would really deadlock my application.

Thanks again for all of the great support.