id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
7796	Memory leak in condition_variable	zhnmju123@…	viboes	"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"	Bugs	closed		thread	Boost 1.52.0	Regression	duplicate