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    <p>You still need mutexes and conditions. Joining a thread makes one thread of execution wait for another thread to finish running. You still need mutexes to protect shared resources. It allows main() in this example to wait for all threads to finish before quitting itself.</p> <pre><code>#include &lt;iostream&gt; #include &lt;thread&gt; #include &lt;chrono&gt; #include &lt;mutex&gt; using namespace std; int global_counter = 0; std::mutex counter_mutex; void five_thread_fn(){ for(int i = 0; i&lt;5; i++){ counter_mutex.lock(); global_counter++; counter_mutex.unlock(); std::cout &lt;&lt; "Updated from five_thread" &lt;&lt; endl; std::this_thread::sleep_for(std::chrono::seconds(5)); } //When this thread finishes we wait for it to join } void ten_thread_fn(){ for(int i = 0; i&lt;10; i++){ counter_mutex.lock(); global_counter++; counter_mutex.unlock(); std::cout &lt;&lt; "Updated from ten_thread" &lt;&lt; endl; std::this_thread::sleep_for(std::chrono::seconds(1)); } //When this thread finishes we wait for it to join } int main(int argc, char *argv[]) { std::cout &lt;&lt; "starting thread ten..." &lt;&lt; std::endl; std::thread ten_thread(ten_thread_fn); std::cout &lt;&lt; "Running ten thread" &lt;&lt; endl; std::thread five_thread(five_thread_fn); ten_thread.join(); std::cout &lt;&lt; "Ten Thread is done." &lt;&lt; std::endl; five_thread.join(); std::cout &lt;&lt; "Five Thread is done." &lt;&lt; std::endl; } </code></pre> <p>Note that the output might look like this:</p> <pre><code>starting thread ten... Running ten thread Updated frUopmd atteend_ tfhrroema df ive_thread Updated from ten_thread Updated from ten_thread Updated from ten_thread Updated from ten_thread Updated from five_thread Updated from ten_thread Updated from ten_thread Updated from ten_thread Updated from ten_thread Updated from ten_thread Updated from five_thread Ten Thread is done. Updated from five_thread Updated from five_thread Five Thread is done. </code></pre> <p>Since std::cout is a shared resource access and use of it should also be mutex protected too.</p>
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    1. POWhat does std::thread.join() do?
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    1. POWhat does std::thread.join() do?
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    1. COThank you Joel, so here ten_thread.join() would tell the program ten_thread is done, and can go to the next step?
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    2. COthe thread of execution running main() will block at the call of ten_thread.join() until ten_thread returns. Once the ten_thread execution ends main's execution is allowed to proceed. Hope this helps.
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