[Boost-bugs] [Boost C++ Libraries] #7796: Memory leak in condition_variable

Subject: [Boost-bugs] [Boost C++ Libraries] #7796: Memory leak in condition_variable
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-12-14 12:28:03

#7796: Memory leak in condition_variable
------------------------------+---------------------------------------------
 Reporter:  zhnmju123@…       |       Owner:  anthonyw  
     Type:  Bugs              |      Status:  new       
Milestone:  To Be Determined  |   Component:  threads   
  Version:  Boost 1.52.0      |    Severity:  Regression
 Keywords:                    |  
------------------------------+---------------------------------------------
 Hi,

 an internal structure within condition_variable keeps growing and so does
 CPU consumption, until it brings my application to a crawl.

 My analysis:

 The follwing change in the recent boost version is responsible:
 boost/thread/win32/condition_variable.hpp:

 Now: (boost 1.52)
 {{{
         ~entry_manager()
         {
             if (! entry->is_notified())
             {
                 entry->remove_waiter();
             }
         }
 }}}


 Before: (boost 1.51)
 {{{
       ~entry_manager()
                 {
                     entry->remove_waiter();
                 }
 }}}

 Result:
 basic_condition_variable::generations keeps growing endlessly; source:
 {{{
 class basic_condition_variable
 {
     entry_ptr get_wait_entry()
     {
 [...]
             entry_ptr new_entry(new list_entry(wake_sem));
 [...]
 };
 }}}


 My test code:
 {{{
 //producer:
     void setWorkload(const std::vector<Zstring>& newLoad) //context of
 main thread
     {
         {
             boost::unique_lock<boost::mutex> dummy(lockFiles);
             filesToLoad = newLoad;
         }

         conditionNewFiles.notify_one();
     }

 //consumer
     Zstring extractNextFile() //context of worker thread, blocking
     {
         boost::unique_lock<boost::mutex> dummy(lockFiles);

         while (filesToLoad.empty())
             conditionNewFiles.timed_wait(dummy,
 boost::posix_time::milliseconds(50)); //interruption point!

         Zstring fileName = filesToLoad.back();
         filesToLoad.pop_back();
         return fileName;
     }

 }}}


 Expectation:
 conditionNewFiles.timed_wait() should not increase
 "basic_condition_variable::generations"!


 Test to verify this bug:

 Using "conditionNewFiles.notify_all()" instead of
 "conditionNewFiles.notify_one()" let's my application behave correctly
 without growing CPU consumption; internal table
 "basic_condition_variable::generations" has one entry.

 Regards, Zenju

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7796>
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