id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
5727,race condition between ~basic_condition_variable() and notify_all(),sbear.powell@…,viboes,"I was writing a quick parfor function when I found this. I think there's a race between ~basic_condition_variable() and notify_all() (notify_one() hasn't failed for me). The following code fails an assertion on my platform (32 bit MSVC 2010):
{{{
void foo() {
    condition_variable notifier;
    mutex m, m2;
    mutex::scoped_lock lock(m);
    bool done=false;
    thread t([&]{
        mutex::scoped_lock lock(m);
        done = true;
        lock.unlock();
        notifier.notify_all();
    });
    while(!done) notifier.wait(lock);
}
}}}

{{{
""Assertion failed: CloseHandle(handle_to_manage), file c:\boost_1_46_1\boost\thread\win32\thread_primitives.hpp, line 237""
}}}


A more detailed stack trace says the exception comes from the worker thread at:

{{{
boost::detail::win32::handle_manager::cleanup() boost\thread\win32\thread_primitives.hpp 237: BOOST_VERIFY(CloseHandle(handle_to_manage));
boost::detail::win32::handle_manager::operator=(void * new_handle=0x00000000)  boost\thread\win32\thread_primitives.hpp 251: cleanup();
boost::detail::basic_condition_variable::notify_all()  boost\thread\win32\condition_variable.hpp 288: wake_sem=detail::win32::handle(0);
notifier.notify_all();
...
}}}

My workaround is to add a second mutex to keep foo() from returning before notify_all() has returned:

{{{
void foo() {
    condition_variable notifier;
    mutex m, m2;
    mutex::scoped_lock lock(m);
    bool done=false;
    thread t([&]{
        mutex::scoped_lock lock(m);
        mutex::scoped_lock lock2(m2);
        done = true;
        lock.unlock();
        notifier.notify_all();
    });
    while(!done) notifier.wait(lock);
    mutex::scoped_lock lock2(m2);
}
}}}

I think (haven't tested) that the real fix is to lock basic_condition_variable's internal_mutex in ~basic_condition_variable() so that it will block until any concurrently running member functions have finished. (an educated guess... this is the first time I've looked at the guts of boost.thread)",Bugs,closed,To Be Determined,thread,Boost 1.46.1,Problem,invalid,,viboes