https://buvidk1234.github.io/tags/channel/Recent content in Channel on 我的技术博客Hugozh-cnTue, 18 Aug 2026 00:17:00 +0800https://buvidk1234.github.io/posts/go-runtime-08-channel-select/Tue, 18 Aug 2026 00:17:00 +0800https://buvidk1234.github.io/posts/go-runtime-08-channel-select/<blockquote> <p>本文源码基线为 <strong>Go 1.26.2、Linux/amd64</strong>。Channel 的语言语义跨平台一致；文中的字段、函数和行号固定到该版本，后续版本可能调整实现。</p> </blockquote> <p>Channel 不是“带锁队列”的同义词。它同时实现值传递、goroutine 阻塞与唤醒、<code>close</code> 广播、<code>select</code> 多路竞争，并且要和栈复制、GC、race detector、Timer 配合。</p> <p>理解 Channel 的关键，是区分三种正常数据路径：直接交接、环形缓冲区、等待队列。前两条可以立即完成；进入等待队列才会把当前 G 变为 <code>_Gwaiting</code>。nil Channel 的阻塞操作是没有数据路径的永久 park，属于另一个边界情况。</p> <h2 id="从语法到runtime入口">从语法到runtime入口</h2> <p>编译器把普通发送和接收分别降低为 <code>runtime.chansend1</code>、<code>runtime.chanrecv1/2</code>。非阻塞的单 case <code>select</code> 会被优化为 <code>selectnbsend</code> 或 <code>selectnbrecv</code>；多个有效 case 才构造 case 数组并调用 <code>runtime.selectgo</code>。</p> <details class="code-fold" open> <summary>GO</summary><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-go" data-lang="go"><span class="line"><span class="cl"><span class="nx">ch</span><span class="w"> </span><span class="o">&lt;-</span><span class="w"> </span><span class="nx">x</span><span class="w"> </span><span class="c1">// runtime.chansend1</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="nx">x</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="o">&lt;-</span><span class="nx">ch</span><span class="w"> </span><span class="c1">// runtime.chanrecv1</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="nx">x</span><span class="p">,</span><span class="w"> </span><span class="nx">ok</span><span class="w"> </span><span class="p">=</span><span class="w"> </span><span class="o">&lt;-</span><span class="nx">ch</span><span class="w"> </span><span class="c1">// runtime.chanrecv2</span><span class="w"> </span></span></span><span class="line"><span class="cl"><span class="nb">close</span><span class="p">(</span><span class="nx">ch</span><span class="p">)</span><span class="w"> </span><span class="c1">// runtime.closechan</span></span></span></code></pre></div></details> <p>这意味着 <code>select</code> 不是对每个 case 依次执行一次普通 channel 操作。它必须在所有相关 Channel 锁的保护下完成一次原子决策。</p> <p>源码入口：<a href="https://github.com/golang/go/blob/go1.26.2/src/cmd/compile/internal/walk/select.go#L56"><code>walk/select.go</code></a> 与 <a href="https://github.com/golang/go/blob/go1.26.2/src/runtime/chan.go#L159"><code>chan.go</code></a>。</p> <h2 id="hchan保存什么">hchan保存什么</h2> <p><a href="https://github.com/golang/go/blob/go1.26.2/src/runtime/chan.go#L34"><code>hchan</code></a> 是 Channel 的运行时对象：</p>