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POHow to force execution of a different thread
 

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    <p>I have one main thread that does some rather CPU intensive operation. The thread has to hold a lock for all its calculations.</p> <p>Then there are some other threads which occasionally require the same lock for brief amounts of time.</p> <p>How can I force the main the main thread to occasionally allow the other threads to execute without slowing it down if there are no other threads?</p> <p>A periodic</p> <pre><code>lock.release() time.sleep(x) lock.acquire() </code></pre> <p>for some x would pass control to another thread, but slow the main thread down if there are no other threads.</p> <p>On the other hand, without the <code>sleep()</code> call the GIL seems to interfere here. Since the main thread has the GIL when it executes <code>release()</code>, the other thread is apparently not able to return from <code>acquire()</code> immediately. Therefore, the main thread continues with its own <code>acquire()</code> method and the other threads never get the lock unless a GIL switch happens to coincide exactly with me releasing my own lock.</p> <p>What's the proper solution for this problem? Is there a way to force a GIL release? Basically I want some magic piece of code that makes sure that in the following test script the second thread always gets the lock first:</p> <pre><code>import threading import time class t1 (threading.Thread): def run(self): print "Second thread waiting for lock" lock.acquire() print "Second thread got lock" lock.release() lock = threading.Lock() lock.acquire() t = t1() t.start() time.sleep(1) lock.release() time.sleep(0) # this works very often, but not all the time lock.acquire() print "Main thread got lock" lock.release() </code></pre>
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