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    <p>I'm going to make a few assumptions because, as more knowledgable people than me have pointed out, this kind of behavior immediately raises the question of <em>why</em> you (think you) need to destroy/recreate these threads, and why this is as obfuscated as it is:</p> <ul> <li>You have a valid reason for needing to destroy/recreate the threads</li> <li>You have a valid reason for adding this many possibly useless layers to the thread creation process</li> <li>Your code which will "receive a message from the other user agent" has access to the thread ids</li> <li>Your <code>send</code> and <code>recv</code> functions can have access to some sort of flagging mechanism</li> </ul> <p>This is such a shoe-horn approach that I'm almost afraid to approach it. Without knowing more about the constraints of your design, it's difficult to express more than some of the options you <em>can</em> start exploring.</p> <p>First, let's set up the <code>send</code> and <code>recv</code> functions so that they can be notified that it's time to go bye-bye:</p> <pre><code>void* send_thread(void *arg) { pthread_mutex_lock(&amp;wrapUpFlagMutex); bool timeToQuit = wrapUpFlag; pthread_mutex_unlock(&amp;wrapUpFlagMutex); while( timeToQuit == false ) { ... // You're doing something here ... pthread_mutex_lock(&amp;wrapUpFlagMutex); timeToQuit = wrapUpFlag; pthread_mutex_unlock(&amp;wrapUpFlagMutex); } // We've been flagged! Get out...the join will catch us. pthread_exit(); } </code></pre> <p>Now change the code which somehow knows when the magic needs to end and be restarted:</p> <pre><code>dontShootTheMessenger() { ... // We've just determined that those threads need to be restarted // Flag those functions to wrap it up pthread_mutex_lock(&amp;wrapUpFlagMutex); wrapUpFlag = true; pthread_mutex_unlock(&amp;wrapUpFlagMutex); // Join the threads, note that this will block pthread_join(thread3, NULL); pthread_join(thread2, NULL); pthread_join(thread1, NULL); // Flag those functions to...not...wrap it up pthread_mutex_lock(&amp;wrapUpFlagMutex); wrapUpFlag = false; pthread_mutex_unlock(&amp;wrapUpFlagMutex); // Launch those puppies again pthread_create(thread1, NULL, first_thread, NULL); ... } </code></pre> <p>Again, this is a mimimalist approach. A more robust method will probably involve conditional variables, a redesign of your calling structure, actually using the passed arguments to the thread functions and return values for <code>pthread_exit()</code>, and much more.</p> <p>Also, depending on your contraints, you may be interested in functionality like <a href="http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_kill.3.html" rel="nofollow">pthread_kill</a>. Note that whatever road you go down, you're not saving yourself any trouble by just hoping that the act of killing off threads somehow cleans things up for you.</p>
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