77 lines
4.9 KiB
HTML
77 lines
4.9 KiB
HTML
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<?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.Title" content="Space location locks" />
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<meta name="abstract" content="A space location lock puts a logical lock on any single byte of storage. The lock does not change the storage or effect your application's access to the storage. The lock is a piece of information recorded by the system." />
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<meta name="description" content="A space location lock puts a logical lock on any single byte of storage. The lock does not change the storage or effect your application's access to the storage. The lock is a piece of information recorded by the system." />
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<meta name="DC.Relation" scheme="URI" content="rzahwe16rx.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Space location locks</title>
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</head>
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<body id="rzahwsll-sllco"><a name="rzahwsll-sllco"><!-- --></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">Space location locks</h1>
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<div><p>A space location lock puts a logical lock on any single byte of
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storage. The lock does not change the storage or effect your application's
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access to the storage. The lock is a piece of information recorded
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by the system.</p>
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<div class="section"><p>Space location locks provide cooperative locking
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similar to that provided by mutual exclusion (mutexes). However, space location
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locks differ from mutexes in several respects: </p>
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<ul><li>You can use the space location lock directly on the data it is protecting.
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The space location lock does not require your application to create and maintain
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an additional object. Correct results in your application still depend on
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the fact that all threads that are accessing the data use the space location
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lock. </li>
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<li>Space location locks allow an application to coordinate the use of different
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locking request types. For example, more than one thread can use space location
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locks to acquire a shared lock on the same data. </li>
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<li>Due to the extra lock types that are provided by space location locks,
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the concept of an owner is slightly different than with mutexes. There can
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be multiple owners of a shared lock if each owner has successfully acquired
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the shared lock. For a thread to get an exclusive lock, all of the shared
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locks must be unlocked. </li>
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<li>Space location locks have different performance implications to your application
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than mutexes. A space location lock costs about 500 reduced instruction set
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computer (RISC) instructions to lock in a path without contention between
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other threads. A mutex costs about 50 RISC instructions in the same path.
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However, a space location lock has no creation or deletion costs associated
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with it, while a mutex costs approximately 1000 RISC instructions for creation
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or deletion.</li>
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</ul>
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</div>
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<div class="section"><div class="p"> <div class="note"><span class="notetitle">Note:</span> Java™ does not have the ability to directly
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use space location locks. Space location locks require the use of pointers.</div>
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</div>
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</div>
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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="rzahwe16rx.htm">Example: Space location locks in Pthread programs</a></strong><br />
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This example shows a Pthread program that is dynamically initializing an integer using the space location lock synchronization primitive.</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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</html>
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