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<li class="toctree-l2 current current-page"><a class="current reference internal" href="#">chapter8 练习</a></li>
|
||
</ul>
|
||
</li>
|
||
</ul>
|
||
<p class="caption" role="heading"><span class="caption-text">附录</span></p>
|
||
<ul>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-a/index.html">附录 A：Rust 系统编程资料</a><input class="toctree-checkbox" id="toctree-checkbox-17" name="toctree-checkbox-17" role="switch" type="checkbox"/><label for="toctree-checkbox-17"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-b/index.html">附录 B：常见工具的使用方法</a><input class="toctree-checkbox" id="toctree-checkbox-18" name="toctree-checkbox-18" role="switch" type="checkbox"/><label for="toctree-checkbox-18"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../appendix-c/index.html">附录 C：深入机器模式：RustSBI</a><input class="toctree-checkbox" id="toctree-checkbox-19" name="toctree-checkbox-19" role="switch" type="checkbox"/><label for="toctree-checkbox-19"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1"><a class="reference internal" href="../appendix-d/index.html">附录 D：RISC-V相关信息</a></li>
|
||
</ul>
|
||
<p class="caption" role="heading"><span class="caption-text">开发注记</span></p>
|
||
<ul>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../setup-sphinx.html">修改和构建本项目</a><input class="toctree-checkbox" id="toctree-checkbox-20" name="toctree-checkbox-20" role="switch" type="checkbox"/><label for="toctree-checkbox-20"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
||
</ul>
|
||
</li>
|
||
<li class="toctree-l1 has-children"><a class="reference internal" href="../rest-example.html">reStructuredText 基本语法</a><input class="toctree-checkbox" id="toctree-checkbox-21" name="toctree-checkbox-21" role="switch" type="checkbox"/><label for="toctree-checkbox-21"><div class="visually-hidden">Toggle child pages in navigation</div><i class="icon"><svg><use href="#svg-arrow-right"></use></svg></i></label><ul class="simple">
|
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</ul>
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</li>
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||
</ul>
|
||
|
||
</div>
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</div>
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</div>
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||
|
||
</div>
|
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</aside>
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<div class="main">
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<div class="content">
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<article role="main">
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<div class="content-icon-container">
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<div class="theme-toggle-container theme-toggle-content">
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<button class="theme-toggle">
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<div class="visually-hidden">Toggle Light / Dark / Auto color theme</div>
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<svg class="theme-icon-when-auto"><use href="#svg-sun-half"></use></svg>
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<svg class="theme-icon-when-dark"><use href="#svg-moon"></use></svg>
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<svg class="theme-icon-when-light"><use href="#svg-sun"></use></svg>
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</button>
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</div>
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<label class="toc-overlay-icon toc-content-icon" for="__toc">
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<div class="visually-hidden">Toggle table of contents sidebar</div>
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<i class="icon"><svg><use href="#svg-toc"></use></svg></i>
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</label>
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</div>
|
||
<div class="section" id="chapter8">
|
||
<h1>chapter8 练习<a class="headerlink" href="#chapter8" title="永久链接至标题">¶</a></h1>
|
||
<div class="section" id="lab5">
|
||
<h2>Lab5 编程作业<a class="headerlink" href="#lab5" title="永久链接至标题">¶</a></h2>
|
||
<div class="admonition warning">
|
||
<p class="admonition-title">警告</p>
|
||
<p>本次实验框架变动较大，且改动较为复杂，为降低同学们的工作量，本次实验不要求合并之前的实验内容，
|
||
只需通过 ch8 的全部测例和其他章节的基础测例即可。你可以参考 <a class="reference external" href="https://github.com/LearningOS/rust-based-os-comp2022/tree/main/os8-ref">lab5(os8)参考框架:</a> 上完成以下作业。</p>
|
||
</div>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">注解</p>
|
||
<p>本次实验的工作量约为 100 行代码。</p>
|
||
</div>
|
||
<div class="section" id="id1">
|
||
<h3>死锁检测<a class="headerlink" href="#id1" title="永久链接至标题">¶</a></h3>
|
||
<p>目前的 mutex 和 semaphore 相关的系统调用不会分析资源的依赖情况，用户程序可能出现死锁。
|
||
我们希望在系统中加入死锁检测机制，当发现可能发生死锁时拒绝对应的资源获取请求。
|
||
一种检测死锁的算法如下：</p>
|
||
<p>定义如下三个数据结构：</p>
|
||
<ul class="simple">
|
||
<li><p>可利用资源向量 Available ：含有 m 个元素的一维数组，每个元素代表可利用的某一类资源的数目，
|
||
其初值是该类资源的全部可用数目，其值随该类资源的分配和回收而动态地改变。
|
||
Available[j] = k，表示第 j 类资源的可用数量为 k。</p></li>
|
||
<li><p>分配矩阵 Allocation：n * m 矩阵，表示每类资源已分配给每个线程的资源数。
|
||
Allocation[i,j] = g，则表示线程 i 当前己分得第 j 类资源的数量为 g。</p></li>
|
||
<li><p>需求矩阵 Need：n * m 的矩阵，表示每个线程还需要的各类资源数量。
|
||
Need[i,j] = d，则表示线程 i 还需要第 j 类资源的数量为 d 。</p></li>
|
||
</ul>
|
||
<p>算法运行过程如下：</p>
|
||
<ol class="arabic simple">
|
||
<li><p>设置两个向量: 工作向量 Work，表示操作系统可提供给线程继续运行所需的各类资源数目，它含有
|
||
m 个元素。初始时，Work = Available ；结束向量 Finish，表示系统是否有足够的资源分配给线程，
|
||
使之运行完成。初始时 Finish[0..n-1] = false，表示所有线程都没结束；当有足够资源分配给线程时，
|
||
设置 Finish[i] = true。</p></li>
|
||
<li><p>从线程集合中找到一个能满足下述条件的线程</p></li>
|
||
</ol>
|
||
<div class="highlight-Rust notranslate"><div class="highlight"><pre><span></span><span class="linenos">1</span>Finish[i] == false;
|
||
<span class="linenos">2</span>Need[i,j] ≤ Work[j];
|
||
</pre></div>
|
||
</div>
|
||
<p>若找到，执行步骤 3，否则执行步骤 4。</p>
|
||
<ol class="arabic simple" start="3">
|
||
<li><p>当线程 thr[i] 获得资源后，可顺利执行，直至完成，并释放出分配给它的资源，故应执行:</p></li>
|
||
</ol>
|
||
<div class="highlight-Rust notranslate"><div class="highlight"><pre><span></span><span class="linenos">1</span><span class="n">Work</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Work</span><span class="p">[</span><span class="n">j</span><span class="p">]</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">Allocation</span><span class="p">[</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">j</span><span class="p">];</span><span class="w"></span>
|
||
<span class="linenos">2</span><span class="n">Finish</span><span class="p">[</span><span class="n">i</span><span class="p">]</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">true</span><span class="p">;</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
<p>跳转回步骤2</p>
|
||
<ol class="arabic simple" start="4">
|
||
<li><p>如果 Finish[0..n-1] 都为 true，则表示系统处于安全状态；否则表示系统处于不安全状态，即出现死锁。</p></li>
|
||
</ol>
|
||
<p>出于兼容性和灵活性考虑，我们允许进程按需开启或关闭死锁检测功能。为此我们将实现一个新的系统调用：
|
||
<code class="docutils literal notranslate"><span class="pre">sys_enable_deadlock_detect</span></code> 。</p>
|
||
<p><strong>enable_deadlock_detect</strong>：</p>
|
||
<ul class="simple">
|
||
<li><p>syscall ID: 469</p></li>
|
||
<li><p>功能：为当前进程启用或禁用死锁检测功能。</p></li>
|
||
<li><p>C 接口： <code class="docutils literal notranslate"><span class="pre">int</span> <span class="pre">enable_deadlock_detect(int</span> <span class="pre">is_enable)</span></code></p></li>
|
||
<li><p>Rust 接口： <code class="docutils literal notranslate"><span class="pre">fn</span> <span class="pre">enable_deadlock_detect(is_enable:</span> <span class="pre">i32)</span> <span class="pre">-></span> <span class="pre">i32</span></code></p></li>
|
||
<li><dl class="simple">
|
||
<dt>参数：</dt><dd><ul>
|
||
<li><p>is_enable: 为 1 表示启用死锁检测， 0 表示禁用死锁检测。</p></li>
|
||
</ul>
|
||
</dd>
|
||
</dl>
|
||
</li>
|
||
<li><dl class="simple">
|
||
<dt>说明：</dt><dd><ul>
|
||
<li><p>开启死锁检测功能后， <code class="docutils literal notranslate"><span class="pre">mutex_lock</span></code> 和 <code class="docutils literal notranslate"><span class="pre">semaphore_down</span></code> 如果检测到死锁，
|
||
应拒绝相应操作并返回 -0xDEAD (十六进制值)。</p></li>
|
||
<li><p>简便起见可对 mutex 和 semaphore 分别进行检测，无需考虑二者 (以及 <code class="docutils literal notranslate"><span class="pre">waittid</span></code> 等)
|
||
混合使用导致的死锁。</p></li>
|
||
</ul>
|
||
</dd>
|
||
</dl>
|
||
</li>
|
||
<li><p>返回值：如果出现了错误则返回 -1，否则返回 0。</p></li>
|
||
<li><dl class="simple">
|
||
<dt>可能的错误</dt><dd><ul>
|
||
<li><p>参数不合法</p></li>
|
||
<li><p>死锁检测开启失败</p></li>
|
||
</ul>
|
||
</dd>
|
||
</dl>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<div class="section" id="id2">
|
||
<h3>实验要求<a class="headerlink" href="#id2" title="永久链接至标题">¶</a></h3>
|
||
<ul class="simple">
|
||
<li><p><a class="reference external" href="https://github.com/LearningOS/rust-based-os-comp2022/tree/main/os8-ref">lab5(os8)参考框架:</a></p></li>
|
||
<li><p>实验目录在 <code class="docutils literal notranslate"><span class="pre">os8</span></code> 。</p></li>
|
||
<li><p>开发并通过所有测例</p></li>
|
||
</ul>
|
||
<p>在 <code class="docutils literal notranslate"><span class="pre">YOUR_LAB5_REPO_DIR</span></code> 下进行编码（可学习参考 <code class="docutils literal notranslate"><span class="pre">os8-ref/src</span></code> 目录下的源代码，并在 <code class="docutils literal notranslate"><span class="pre">os8/src</span></code> 中完成编码），并进行编译测试。</p>
|
||
<div class="admonition note">
|
||
<p class="admonition-title">注解</p>
|
||
<p><strong>测试方式</strong></p>
|
||
<p>你的实现只需且必须通过测例，建议读者感到困惑时先检查测例</p>
|
||
<p>如果实现正确，可在项目仓库的根目录下执行 <code class="docutils literal notranslate"><span class="pre">make</span> <span class="pre">test8</span></code> ，应该看到类似如下的显示输出：</p>
|
||
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span><span class="nb">cd</span> YOUR_LAB5_REPO_DIR
|
||
<span class="gp">$ </span>make test8
|
||
<span class="go">......</span>
|
||
<span class="go">[rustsbi] RustSBI version 0.2.2, adapting to RISC-V SBI v1.0.0</span>
|
||
<span class="go">.______ __ __ _______.___________. _______..______ __</span>
|
||
<span class="go">| _ \ | | | | / | | / || _ \ | |</span>
|
||
<span class="go">| |_) | | | | | | (----`---| |----`| (----`| |_) || |</span>
|
||
<span class="go">| / | | | | \ \ | | \ \ | _ < | |</span>
|
||
<span class="go">| |\ \----.| `--' |.----) | | | .----) | | |_) || |</span>
|
||
<span class="go">| _| `._____| \______/ |_______/ |__| |_______/ |______/ |__|</span>
|
||
<span class="go">[rustsbi] Implementation : RustSBI-QEMU Version 0.1.1</span>
|
||
<span class="go">[rustsbi] Platform Name : riscv-virtio,qemu</span>
|
||
<span class="go">[rustsbi] Platform SMP : 1</span>
|
||
<span class="go">[rustsbi] Platform Memory : 0x80000000..0x88000000</span>
|
||
<span class="go">[rustsbi] Boot HART : 0</span>
|
||
<span class="go">[rustsbi] Device Tree Region : 0x87000000..0x87000ef2</span>
|
||
<span class="go">[rustsbi] Firmware Address : 0x80000000</span>
|
||
<span class="go">[rustsbi] Supervisor Address : 0x80200000</span>
|
||
<span class="go">[rustsbi] pmp01: 0x00000000..0x80000000 (-wr)</span>
|
||
<span class="go">[rustsbi] pmp02: 0x80000000..0x80200000 (---)</span>
|
||
<span class="go">[rustsbi] pmp03: 0x80200000..0x88000000 (xwr)</span>
|
||
<span class="go">......</span>
|
||
<span class="go">[PASS] found <Hello, world from user mode program!></span>
|
||
<span class="go">[PASS] found <Test power_3 OK60963!></span>
|
||
<span class="go">[PASS] found <Test power_5 OK60963!></span>
|
||
<span class="go">......</span>
|
||
<span class="go">[PASS] found <threads test passed60963!></span>
|
||
<span class="go">[PASS] found <deadlock test mutex 1 OK60963!></span>
|
||
<span class="go">[PASS] found <deadlock test semaphore 1 OK60963!></span>
|
||
<span class="go">[PASS] found <deadlock test semaphore 2 OK60963!></span>
|
||
<span class="go">[PASS] found <ch8 Usertests passed60963!></span>
|
||
<span class="go">[PASS] not found <FAIL: T.T></span>
|
||
<span class="go">[PASS] not found <Should cause error, Test 04_2 fail!></span>
|
||
<span class="go">[PASS] not found <Should cause error, Test 04_3 fail!></span>
|
||
|
||
<span class="go">Test passed60963: 29/29</span>
|
||
<span class="go">Report for lab1 found.</span>
|
||
<span class="go">Report for lab2 found.</span>
|
||
<span class="go">Report for lab3 found.</span>
|
||
<span class="go">Report for lab4 found.</span>
|
||
<span class="go">Report for lab5 found.</span>
|
||
</pre></div>
|
||
</div>
|
||
</div>
|
||
<ul>
|
||
<li><p>提交你的修改</p>
|
||
<blockquote>
|
||
<div><ul class="simple">
|
||
<li><p>如果是基于GitHub Classroom 开发, 在本地环境或在线codespaces环境下，执行 <code class="docutils literal notranslate"><span class="pre">git</span> <span class="pre">push</span></code> 命令，提交修改的代码到gitub进行CI自动评测。如果评测结果是 红色小叉 （位于repo的中上位置），可进一步点击红色小叉查找具体出错时的CI执行情况。</p></li>
|
||
</ul>
|
||
</div></blockquote>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="section" id="id4">
|
||
<h2>问答作业<a class="headerlink" href="#id4" title="永久链接至标题">¶</a></h2>
|
||
<ol class="arabic simple">
|
||
<li><p>在我们的多线程实现中，当主线程 (即 0 号线程) 退出时，视为整个进程退出，
|
||
此时需要结束该进程管理的所有线程并回收其资源。
|
||
- 需要回收的资源有哪些？
|
||
- 其他线程的 TaskControlBlock 可能在哪些位置被引用，分别是否需要回收，为什么？</p></li>
|
||
<li><p>对比以下两种 <code class="docutils literal notranslate"><span class="pre">Mutex.unlock</span></code> 的实现，二者有什么区别？这些区别可能会导致什么问题？</p></li>
|
||
</ol>
|
||
<div class="highlight-Rust notranslate"><div class="highlight"><pre><span></span><span class="linenos"> 1</span><span class="k">impl</span><span class="w"> </span><span class="n">Mutex</span><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">Mutex1</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 2</span><span class="w"> </span><span class="k">fn</span> <span class="nf">unlock</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 3</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">mutex_inner</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">inner</span><span class="p">.</span><span class="n">exclusive_access</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos"> 4</span><span class="w"> </span><span class="fm">assert!</span><span class="p">(</span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">locked</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos"> 5</span><span class="w"> </span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos"> 6</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">waking_task</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">wait_queue</span><span class="p">.</span><span class="n">pop_front</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos"> 7</span><span class="w"> </span><span class="n">add_task</span><span class="p">(</span><span class="n">waking_task</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos"> 8</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos"> 9</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">10</span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">11</span>
|
||
<span class="linenos">12</span><span class="k">impl</span><span class="w"> </span><span class="n">Mutex</span><span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="n">Mutex2</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">13</span><span class="w"> </span><span class="k">fn</span> <span class="nf">unlock</span><span class="p">(</span><span class="o">&</span><span class="bp">self</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">14</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="k">mut</span><span class="w"> </span><span class="n">mutex_inner</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">inner</span><span class="p">.</span><span class="n">exclusive_access</span><span class="p">();</span><span class="w"></span>
|
||
<span class="linenos">15</span><span class="w"> </span><span class="fm">assert!</span><span class="p">(</span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">locked</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">16</span><span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">waking_task</span><span class="p">)</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">wait_queue</span><span class="p">.</span><span class="n">pop_front</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">17</span><span class="w"> </span><span class="n">add_task</span><span class="p">(</span><span class="n">waking_task</span><span class="p">);</span><span class="w"></span>
|
||
<span class="linenos">18</span><span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
|
||
<span class="linenos">19</span><span class="w"> </span><span class="n">mutex_inner</span><span class="p">.</span><span class="n">locked</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="kc">false</span><span class="p">;</span><span class="w"></span>
|
||
<span class="linenos">20</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">21</span><span class="w"> </span><span class="p">}</span><span class="w"></span>
|
||
<span class="linenos">22</span><span class="p">}</span><span class="w"></span>
|
||
</pre></div>
|
||
</div>
|
||
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|
||
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|
||
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