[boost] [ASIO] Issue with epoll reactor? Callback handler not executed.

Subject: [boost] [ASIO] Issue with epoll reactor? Callback handler not executed.
From: Arpan Sen (arpansen_at_[hidden])
Date: 2013-05-23 15:15:57

Hi folks,

I am using the latest version of Boost ASIO on a Suse11 box. I recently
upgraded from an older version of Boost, and life since then has been
unusually harsh.
****

I have a piece of ASIO code that worked just fine earlier but doesn't do so
now. Here's the offending snippet, rather simple looking: ****

   boost::asio::streambuf response;

   ... // code for deadline timer

   tcp::socket socket(io_service);

   socket.async_connect(*iterator, &conn_handler);

   io_service.reset();

   io_service.run_one();

   async_write(socket, buffer(command.c_str()), &write_handler);

   io_service.reset();

   io_service.run_one();

   async_read_until(socket, response, '\n', &read_handler);

   io_service.reset();

   io_service.run_one();

Everything works fine till async_write.

During async_read_until I can see that the response buffer does have
some data by the time it returns. However, when io_service.run_one()
happens the read_handler is NOT ALWAYS called which is very
surprising. The function calling the read_handler (internal to ASIO)
also does a commit to the streambuf so streambuf.size() becomes
non-zero, i.e. ready for  consumption by something like istream. All
of that is missing now.

Debugging this in some detail, I see that run_one is in fact
responsible for calling read_handler. That is NOT  happening and in
epoll_reactor I am not seeing any real activity. Something there is
activity and the behavior is as expected but 9/10 times completion
handler won’t be called. The io_service object runs in a specific
thread (I have a bunch of threads in my app) and no other thread
accesses it.

The Linux kernel running previous version has not been changed when I
upgraded the Boost libraries.

Instead of epoll, if I use select everything looks good. Any thoughts?

Arpan