blocking on the main thread

[aharondavid]

according to https://emscripten.org/docs/porting/pthreads.html#blocking-on-the-main-browser-thread :
"Busy-waiting on the main browser thread in general will work despite the downsides just mentioned, for things like waiting on a lightly-contended mutex. However, things like pthread_join and pthread_cond_wait are often intended to block for long periods of time, and if that happens on the main browser thread, and while other threads expect it to respond, it can cause a surprising deadlock. That can happen because of proxying, see the previous section. If the main thread blocks while a worker attempts to proxy to it, a deadlock can occur."

is there an example for such potential dead lock?

I execute the following func in the main thread and I am not sure that it safe:

wait_forever(pthread_mutex_t* m) {
	int retval = 0;
    if (m == NULL)
    	m = &m_mutex;
    pthread_mutex_lock(&m_mutex);
    while (this->m_sigobj == (HANDLE)NULL)
		retval = pthread_cond_wait(&m_cond, m);
    pthread_mutex_unlock(&m_mutex);
    return retval;
}