Re: using std::deque in multiple threads

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 15 Aug 2006 17:42:49 -0400

Message-ID:

<uDNn2OLwGHA.4756@TK2MSFTNGP02.phx.gbl>

Create a CRITICAL_SECTION object cs and initialize it
with InitializeCriticalSection(&cs);
Then see code inserted in-line...

PaulH wrote:

I have a thread that listens on a message queue and populates a
std::deque with events from that message queue, but only holds the
latest 100.
In my main thread, I want to populate a listbox with the information
from that deque. So, it ends up being that one thread can add/remove
items from the deque while another thread is trying to iterate through
them. How can I make this thread-safe?

Thanks,
PaulH

The code looks a bit like this:

std::deque<MESSAGE_TYPE> m_dequeMessages;

CMyClass::MessageThread()
{
  //...
  while (ReadMsgQueue(hMsgQueue, &msg,...))
  {

---> EnterCriticalSection(&cs);

    m_dequeMessages.push_back(msg);
    if(m_dequeMessages.size() > 100)
      m_dequeMessages.pop_front();

---> LeaveCriticalSection(&cs);

}
//...
}

CListCtrl c_MyList;

CDlgClass::PopulateList()
{

---> EnterCriticalSection(&cs);

  for (vector::iterator i = m_dequeMessages.begin(),
        i != m_vMessages.end()
        ++i)
  {
    c_MyList.InsertItem(0, i->Message);
  }

---> LeaveCriticalSection(&cs);

}

This will cause one thread to wait (at Enter...) if the other thread is
within the critical section.

--
Scott McPhillips [VC++ MVP]