[Boost-bugs] [Boost C++ Libraries] #4725: Synchronisation and shared mutex's Get total_count

Subject: [Boost-bugs] [Boost C++ Libraries] #4725: Synchronisation and shared mutex's Get total_count
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-10-10 14:48:30

#4725: Synchronisation and shared mutex's Get total_count
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 Reporter:  dominicstreeter@…                         |       Owner:  anthonyw
     Type:  Feature Requests                          |      Status:  new     
Milestone:  To Be Determined                          |   Component:  threads 
  Version:  Boost 1.44.0                              |    Severity:  Problem 
 Keywords:  Synchronisation Barriers Get total_count  |  
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 Hey there I wish to create what is in essence a barrier but with the
 capacity to flexibly dictate how many threads are in the barrier. The
 problem is synchronising.

 Here is an example of the problem that shows I need to get the total count
 of threads accessing the shared total_count variable atomically from the
 boost library. I would like to know if there is a reason this is not
 implemented.

 Here are some variables to demonstrate the issue.

 boost::condition_variable_any multiThreadLinkReady;

 boost::shared_mutex smutDependancyThreadCustomBarrierReady;

 bool boolIsSceneReady;

 //Run by a management thread

 void wakeUpIfAllReady()
 {
      mutAccessData.lock();

      if (intThreadsCaughtCountPost >= TOTALTHREADSLOADINGSCENE)
      {
            if (Here I need to the total count to also equal the Constant
 TOTALTHREADSLOADINGSCENE to garuntee every thread wakes up in a one time
 call to notify all of them into the next stage)

            multiThreadLinkReady.notify_all();

            boolIsSceneReady = true;
      }

      mutAccessData.unlock();
 }

 //Run by every thread but the management thread relating to this data

 void waitUntilAllReady()
 {
      mutAccessData.lock();

      if (boolIsSceneReady == false)
      {
           intThreadsCaughtCountPost++;

           mutAccessData.unlock();

           //The thread is set to frozen to be awoken on the next line when
 the class is ready. It possible for this to not be set before the other
 thread calls notify all!
 multiThreadLinkReady.wait(smutDependancyThreadCustomBarrierReady);

           //So we can reuse this on the next level loaded we need to
 decrement the counter.
           mutAccessData.lock();

           intThreadsCaughtCountPost--;

           mutAccessData.unlock();
      }
      else
      {
           mutAccessData.unlock();
      }
 }

 There is no way of avoiding using interrupts when using the available
 barrier mechanism with a complex system involving alot of states this is
 not always desirable. If a thread were to fail and you needed to bail the
 other threads out of the barrier class you need to do alot more than if
 you can use a conditional variable like this and get the total threads
 that are actively waiting, creating a flexible barrier.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4725>
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