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  28 <a name="intrusive.thread_safety"></a><a class="link" href="thread_safety.html" title="Thread safety guarantees">Thread safety guarantees</a>
  29 </h2></div></div></div>
  30 <p>
  31       Intrusive containers have thread safety guarantees similar to STL containers.
  32     </p>
  33 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  34 <li class="listitem">
  35           Several threads having read or write access to different instances is safe
  36           as long as inserted objects are different.
  37         </li>
  38 <li class="listitem">
  39           Concurrent read-only access to the same container is safe.
  40         </li>
  41 </ul></div>
  42 <p>
  43       Some Intrusive hooks (auto-unlink hooks, for example) modify containers without
  44       having a reference to them: this is considered a write access to the container.
  45     </p>
  46 <p>
  47       Other functions, like checking if an object is already inserted in a container
  48       using the <code class="computeroutput"><span class="identifier">is_linked</span><span class="special">()</span></code>
  49       member of safe hooks, constitute read access on the container without having
  50       a reference to it, so no other thread should have write access (direct or indirect)
  51       to that container.
  52     </p>
  53 <p>
  54       Since the same object can be inserted in several containers at the same time
  55       using different hooks, the thread safety of <span class="bold"><strong>Boost.Intrusive</strong></span>
  56       is related to the containers and also to the object whose lifetime is manually
  57       managed by the user.
  58     </p>
  59 <p>
  60       As we can see, the analysis of the thread-safety of a program using <span class="bold"><strong>Boost.Intrusive</strong></span> is harder than with non-intrusive containers.
  61     </p>
  62 <p>
  63       To analyze the thread safety, consider the following points:
  64     </p>
  65 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  66 <li class="listitem">
  67           The auto-unlink hook's destructor and <code class="computeroutput"><span class="identifier">unlink</span><span class="special">()</span></code> functions modify the container indirectly.
  68         </li>
  69 <li class="listitem">
  70           The safe mode and auto-unlink hooks' <code class="computeroutput"><span class="identifier">is_linked</span><span class="special">()</span></code> functions are a read access to the container.
  71         </li>
  72 <li class="listitem">
  73           Inserting an object in containers that will be modified by different threads
  74           has no thread safety guarantee, although in most platforms it will be thread-safe
  75           without locking.
  76         </li>
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  81 <td align="right"><div class="copyright-footer">Copyright &#169; 2005 Olaf Krzikalla<br>Copyright &#169; 2006-2015 Ion Gaztanaga<p>
  82         Distributed under the Boost Software License, Version 1.0. (See accompanying
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