Re: [Boost-users] problem using boost::condition in Win32

19 Apr 2007

      On 4/19/07, Peter Dimov  wrote:
...
PJ Durai wrote:
...
On 4/18/07, Ken  wrote:
...
On Apr 13, 2007, PJ Durai wrote:
...
...
I have two threads waiting on a condition. When I call
condition::notify_all() from the main thread, I expected both
threads to fall through and proceed simultaneously.
But that is not what I am witnessing.
They behave like I had called condition::notify_one()  twice.
One thread continues, does its thing (in this case a simple Sleep
and a printf) comes back to wait. Only after that point the second
thread continued from the condition.
Is this expected ? What am I missing ?
This is expected. condition::wait reacquires the mutex after it returns. You
then call Sleep(4000) with the mutex locked; the other threads can't
continue because they are waiting for the mutex. Try unlocking lk before
Sleep'ing.
Thanks peter.
That fixed it.
My loop looks like this now. And it is working as expected.

   void operator() ()
   {
      while(1)
      {
         {
            TRACE("%s : waiting ...\n", name.c_str());
            {
               TRACE("%s : before cond wait...\n", name.c_str());
               {
                  boost::mutex::scoped_lock lk(mutex);
                  cond.wait(lk);
               }
               TRACE("%s : after cond wait...\n", name.c_str());
               {
                  TRACE("%s : doing stuff...\n", name.c_str());

                  //ElapsedTime etime(name.c_str());
                  Sleep(4000);
                  for (int i=0; i<10; ++i)
                     std::cout << id;
                  std::cout << std::endl;
               }
            }
         }
         //barrier.wait();
      }
   }

Thanks Guys.