66 lines
4.4 KiB
HTML
66 lines
4.4 KiB
HTML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Condition variables and threads" />
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<meta name="abstract" content="Condition variables allow threads to wait for certain events or conditions to occur and they notify other threads that are also waiting for the same events or conditions." />
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<meta name="description" content="Condition variables allow threads to wait for certain events or conditions to occur and they notify other threads that are also waiting for the same events or conditions." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>Condition variables and threads</title>
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</head>
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<body id="rzahwvar-varco"><a name="rzahwvar-varco"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Condition variables and threads</h1>
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<div><p>Condition variables allow threads to wait for certain events or
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conditions to occur and they notify other threads that are also waiting for
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the same events or conditions.</p>
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<p>The thread can wait on a condition variable and broadcast a condition such
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that one or all of the threads that are waiting on the condition variable
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become active. You can consider condition variables to be similar to using
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events to synchronize threads on other platforms.</p>
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<p>Condition variables do not have ownership associated with them and are
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typically stateless. A stateless condition variable means that if a thread
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signals a condition variable to wake up a waiting thread when there are currently
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no waiting threads, the signal is discarded and no action is
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taken. The signal is effectively lost. It is possible for one thread to signal
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a condition immediately before a different thread begins waiting for it without
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any resulting action. </p>
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<p>Locking protocols that use mutual exclusions (mutexes)
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are typically used with condition variables. If you use locking protocols,
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your application can ensure that a thread does not lose a signal that was
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intended to wake it up.</p>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rzahwe17rx.htm">Example: Use condition variables in Pthread programs</a></strong><br />
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This example shows a Pthread program using condition variables to notify threads of a condition. Notice what mutual exclusion (mutex) locking protocol is used.</li>
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<li class="ulchildlink"><strong><a href="rzahwex5rx.htm">Example: Use condition variables in Java programs</a></strong><br />
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This example shows a Java™ program using condition variables in
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the form of the wait and notify methods on a Java™ object. Note the locking protocol used.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzahwsynco.htm" title="When you create code that is threadsafe but still benefits from sharing data or resources between threads, the most important aspect of programming becomes the ability to synchronize threads.">Synchronization techniques among threads</a></div>
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</div>
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</div>
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</body>
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