How to draw in Cinder concurrently?

Question

I'm trying to launch 4 standard C++ threads, each drawing a line, but an abort() gets called in runtime. I try to adhere to this example, pass over the GL drawing context, use a mutex for thread synchronization. What do I do wrong?

void drawTest(gl::ContextRef _context, vec2 p1, vec2 p2, mutex& latch)
{
    ci::ThreadSetup threadSetup;
    latch.lock();
    _context->makeCurrent();
    gl::drawLine(p1, p2);
    latch.unlock();
}

void Func()
{
   vector<thread> threads;
   mutex myMutex;
   gl::ContextRef backgroundCtx = gl::Context::create(gl::context());
   threads.push_back(thread(drawTest, backgroundCtx, vec2(100, 344), vec2(150, 344), std::ref(myMutex)));
   threads.push_back(thread(drawTest, backgroundCtx, vec2(400, 850), vec2(730, 200), std::ref(myMutex)));
   threads.push_back(thread(drawTest, backgroundCtx, vec2(302, 540), vec2(150, 905), std::ref(myMutex)));
   threads.push_back(thread(drawTest, backgroundCtx, vec2(222, 930), vec2(50, 777), std::ref(myMutex)));
}