| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/git/checkouts/rayon-3b3b152053499ede/a07ce2e/rayon-core/src/latch.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>latch.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../rayon_core/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../rayon_core/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
| <span id="2">2</span> |
| <span id="3">3</span> |
| <span id="4">4</span> |
| <span id="5">5</span> |
| <span id="6">6</span> |
| <span id="7">7</span> |
| <span id="8">8</span> |
| <span id="9">9</span> |
| <span id="10">10</span> |
| <span id="11">11</span> |
| <span id="12">12</span> |
| <span id="13">13</span> |
| <span id="14">14</span> |
| <span id="15">15</span> |
| <span id="16">16</span> |
| <span id="17">17</span> |
| <span id="18">18</span> |
| <span id="19">19</span> |
| <span id="20">20</span> |
| <span id="21">21</span> |
| <span id="22">22</span> |
| <span id="23">23</span> |
| <span id="24">24</span> |
| <span id="25">25</span> |
| <span id="26">26</span> |
| <span id="27">27</span> |
| <span id="28">28</span> |
| <span id="29">29</span> |
| <span id="30">30</span> |
| <span id="31">31</span> |
| <span id="32">32</span> |
| <span id="33">33</span> |
| <span id="34">34</span> |
| <span id="35">35</span> |
| <span id="36">36</span> |
| <span id="37">37</span> |
| <span id="38">38</span> |
| <span id="39">39</span> |
| <span id="40">40</span> |
| <span id="41">41</span> |
| <span id="42">42</span> |
| <span id="43">43</span> |
| <span id="44">44</span> |
| <span id="45">45</span> |
| <span id="46">46</span> |
| <span id="47">47</span> |
| <span id="48">48</span> |
| <span id="49">49</span> |
| <span id="50">50</span> |
| <span id="51">51</span> |
| <span id="52">52</span> |
| <span id="53">53</span> |
| <span id="54">54</span> |
| <span id="55">55</span> |
| <span id="56">56</span> |
| <span id="57">57</span> |
| <span id="58">58</span> |
| <span id="59">59</span> |
| <span id="60">60</span> |
| <span id="61">61</span> |
| <span id="62">62</span> |
| <span id="63">63</span> |
| <span id="64">64</span> |
| <span id="65">65</span> |
| <span id="66">66</span> |
| <span id="67">67</span> |
| <span id="68">68</span> |
| <span id="69">69</span> |
| <span id="70">70</span> |
| <span id="71">71</span> |
| <span id="72">72</span> |
| <span id="73">73</span> |
| <span id="74">74</span> |
| <span id="75">75</span> |
| <span id="76">76</span> |
| <span id="77">77</span> |
| <span id="78">78</span> |
| <span id="79">79</span> |
| <span id="80">80</span> |
| <span id="81">81</span> |
| <span id="82">82</span> |
| <span id="83">83</span> |
| <span id="84">84</span> |
| <span id="85">85</span> |
| <span id="86">86</span> |
| <span id="87">87</span> |
| <span id="88">88</span> |
| <span id="89">89</span> |
| <span id="90">90</span> |
| <span id="91">91</span> |
| <span id="92">92</span> |
| <span id="93">93</span> |
| <span id="94">94</span> |
| <span id="95">95</span> |
| <span id="96">96</span> |
| <span id="97">97</span> |
| <span id="98">98</span> |
| <span id="99">99</span> |
| <span id="100">100</span> |
| <span id="101">101</span> |
| <span id="102">102</span> |
| <span id="103">103</span> |
| <span id="104">104</span> |
| <span id="105">105</span> |
| <span id="106">106</span> |
| <span id="107">107</span> |
| <span id="108">108</span> |
| <span id="109">109</span> |
| <span id="110">110</span> |
| <span id="111">111</span> |
| <span id="112">112</span> |
| <span id="113">113</span> |
| <span id="114">114</span> |
| <span id="115">115</span> |
| <span id="116">116</span> |
| <span id="117">117</span> |
| <span id="118">118</span> |
| <span id="119">119</span> |
| <span id="120">120</span> |
| <span id="121">121</span> |
| <span id="122">122</span> |
| <span id="123">123</span> |
| <span id="124">124</span> |
| <span id="125">125</span> |
| <span id="126">126</span> |
| <span id="127">127</span> |
| <span id="128">128</span> |
| <span id="129">129</span> |
| <span id="130">130</span> |
| <span id="131">131</span> |
| <span id="132">132</span> |
| <span id="133">133</span> |
| <span id="134">134</span> |
| <span id="135">135</span> |
| <span id="136">136</span> |
| <span id="137">137</span> |
| <span id="138">138</span> |
| <span id="139">139</span> |
| <span id="140">140</span> |
| <span id="141">141</span> |
| <span id="142">142</span> |
| <span id="143">143</span> |
| <span id="144">144</span> |
| <span id="145">145</span> |
| <span id="146">146</span> |
| <span id="147">147</span> |
| <span id="148">148</span> |
| <span id="149">149</span> |
| <span id="150">150</span> |
| <span id="151">151</span> |
| <span id="152">152</span> |
| <span id="153">153</span> |
| <span id="154">154</span> |
| <span id="155">155</span> |
| <span id="156">156</span> |
| <span id="157">157</span> |
| <span id="158">158</span> |
| <span id="159">159</span> |
| <span id="160">160</span> |
| <span id="161">161</span> |
| <span id="162">162</span> |
| <span id="163">163</span> |
| <span id="164">164</span> |
| <span id="165">165</span> |
| <span id="166">166</span> |
| <span id="167">167</span> |
| <span id="168">168</span> |
| <span id="169">169</span> |
| <span id="170">170</span> |
| <span id="171">171</span> |
| <span id="172">172</span> |
| <span id="173">173</span> |
| <span id="174">174</span> |
| <span id="175">175</span> |
| <span id="176">176</span> |
| <span id="177">177</span> |
| <span id="178">178</span> |
| <span id="179">179</span> |
| <span id="180">180</span> |
| <span id="181">181</span> |
| <span id="182">182</span> |
| <span id="183">183</span> |
| <span id="184">184</span> |
| <span id="185">185</span> |
| <span id="186">186</span> |
| <span id="187">187</span> |
| <span id="188">188</span> |
| <span id="189">189</span> |
| <span id="190">190</span> |
| <span id="191">191</span> |
| <span id="192">192</span> |
| <span id="193">193</span> |
| <span id="194">194</span> |
| <span id="195">195</span> |
| <span id="196">196</span> |
| <span id="197">197</span> |
| <span id="198">198</span> |
| <span id="199">199</span> |
| <span id="200">200</span> |
| <span id="201">201</span> |
| <span id="202">202</span> |
| <span id="203">203</span> |
| <span id="204">204</span> |
| <span id="205">205</span> |
| <span id="206">206</span> |
| <span id="207">207</span> |
| <span id="208">208</span> |
| <span id="209">209</span> |
| <span id="210">210</span> |
| <span id="211">211</span> |
| <span id="212">212</span> |
| <span id="213">213</span> |
| <span id="214">214</span> |
| <span id="215">215</span> |
| <span id="216">216</span> |
| <span id="217">217</span> |
| <span id="218">218</span> |
| <span id="219">219</span> |
| <span id="220">220</span> |
| <span id="221">221</span> |
| <span id="222">222</span> |
| <span id="223">223</span> |
| <span id="224">224</span> |
| <span id="225">225</span> |
| <span id="226">226</span> |
| <span id="227">227</span> |
| <span id="228">228</span> |
| <span id="229">229</span> |
| <span id="230">230</span> |
| <span id="231">231</span> |
| <span id="232">232</span> |
| <span id="233">233</span> |
| <span id="234">234</span> |
| <span id="235">235</span> |
| <span id="236">236</span> |
| <span id="237">237</span> |
| <span id="238">238</span> |
| <span id="239">239</span> |
| <span id="240">240</span> |
| <span id="241">241</span> |
| <span id="242">242</span> |
| <span id="243">243</span> |
| <span id="244">244</span> |
| <span id="245">245</span> |
| <span id="246">246</span> |
| <span id="247">247</span> |
| <span id="248">248</span> |
| <span id="249">249</span> |
| <span id="250">250</span> |
| <span id="251">251</span> |
| <span id="252">252</span> |
| <span id="253">253</span> |
| <span id="254">254</span> |
| <span id="255">255</span> |
| <span id="256">256</span> |
| <span id="257">257</span> |
| <span id="258">258</span> |
| <span id="259">259</span> |
| <span id="260">260</span> |
| <span id="261">261</span> |
| <span id="262">262</span> |
| <span id="263">263</span> |
| <span id="264">264</span> |
| <span id="265">265</span> |
| <span id="266">266</span> |
| <span id="267">267</span> |
| <span id="268">268</span> |
| <span id="269">269</span> |
| <span id="270">270</span> |
| <span id="271">271</span> |
| <span id="272">272</span> |
| <span id="273">273</span> |
| <span id="274">274</span> |
| <span id="275">275</span> |
| <span id="276">276</span> |
| <span id="277">277</span> |
| <span id="278">278</span> |
| <span id="279">279</span> |
| <span id="280">280</span> |
| <span id="281">281</span> |
| <span id="282">282</span> |
| <span id="283">283</span> |
| <span id="284">284</span> |
| <span id="285">285</span> |
| <span id="286">286</span> |
| <span id="287">287</span> |
| <span id="288">288</span> |
| <span id="289">289</span> |
| <span id="290">290</span> |
| <span id="291">291</span> |
| <span id="292">292</span> |
| <span id="293">293</span> |
| <span id="294">294</span> |
| <span id="295">295</span> |
| <span id="296">296</span> |
| <span id="297">297</span> |
| <span id="298">298</span> |
| <span id="299">299</span> |
| <span id="300">300</span> |
| <span id="301">301</span> |
| <span id="302">302</span> |
| <span id="303">303</span> |
| <span id="304">304</span> |
| <span id="305">305</span> |
| <span id="306">306</span> |
| <span id="307">307</span> |
| <span id="308">308</span> |
| <span id="309">309</span> |
| <span id="310">310</span> |
| <span id="311">311</span> |
| <span id="312">312</span> |
| <span id="313">313</span> |
| <span id="314">314</span> |
| <span id="315">315</span> |
| <span id="316">316</span> |
| <span id="317">317</span> |
| <span id="318">318</span> |
| <span id="319">319</span> |
| <span id="320">320</span> |
| <span id="321">321</span> |
| <span id="322">322</span> |
| <span id="323">323</span> |
| <span id="324">324</span> |
| <span id="325">325</span> |
| <span id="326">326</span> |
| <span id="327">327</span> |
| <span id="328">328</span> |
| <span id="329">329</span> |
| <span id="330">330</span> |
| <span id="331">331</span> |
| <span id="332">332</span> |
| <span id="333">333</span> |
| <span id="334">334</span> |
| <span id="335">335</span> |
| <span id="336">336</span> |
| <span id="337">337</span> |
| <span id="338">338</span> |
| <span id="339">339</span> |
| <span id="340">340</span> |
| <span id="341">341</span> |
| <span id="342">342</span> |
| <span id="343">343</span> |
| <span id="344">344</span> |
| <span id="345">345</span> |
| <span id="346">346</span> |
| <span id="347">347</span> |
| <span id="348">348</span> |
| <span id="349">349</span> |
| <span id="350">350</span> |
| <span id="351">351</span> |
| <span id="352">352</span> |
| <span id="353">353</span> |
| <span id="354">354</span> |
| <span id="355">355</span> |
| <span id="356">356</span> |
| <span id="357">357</span> |
| <span id="358">358</span> |
| <span id="359">359</span> |
| <span id="360">360</span> |
| <span id="361">361</span> |
| <span id="362">362</span> |
| <span id="363">363</span> |
| <span id="364">364</span> |
| <span id="365">365</span> |
| <span id="366">366</span> |
| <span id="367">367</span> |
| <span id="368">368</span> |
| <span id="369">369</span> |
| <span id="370">370</span> |
| <span id="371">371</span> |
| <span id="372">372</span> |
| <span id="373">373</span> |
| <span id="374">374</span> |
| <span id="375">375</span> |
| <span id="376">376</span> |
| <span id="377">377</span> |
| <span id="378">378</span> |
| <span id="379">379</span> |
| <span id="380">380</span> |
| <span id="381">381</span> |
| <span id="382">382</span> |
| <span id="383">383</span> |
| <span id="384">384</span> |
| <span id="385">385</span> |
| <span id="386">386</span> |
| <span id="387">387</span> |
| <span id="388">388</span> |
| <span id="389">389</span> |
| <span id="390">390</span> |
| <span id="391">391</span> |
| <span id="392">392</span> |
| <span id="393">393</span> |
| <span id="394">394</span> |
| <span id="395">395</span> |
| <span id="396">396</span> |
| <span id="397">397</span> |
| <span id="398">398</span> |
| <span id="399">399</span> |
| <span id="400">400</span> |
| <span id="401">401</span> |
| <span id="402">402</span> |
| <span id="403">403</span> |
| <span id="404">404</span> |
| <span id="405">405</span> |
| <span id="406">406</span> |
| <span id="407">407</span> |
| <span id="408">408</span> |
| <span id="409">409</span> |
| <span id="410">410</span> |
| <span id="411">411</span> |
| <span id="412">412</span> |
| <span id="413">413</span> |
| <span id="414">414</span> |
| </pre><pre class="rust"><code><span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::ops::Deref; |
| <span class="kw">use </span>std::sync::atomic::{AtomicUsize, Ordering}; |
| <span class="kw">use </span>std::sync::{Arc, Condvar, Mutex}; |
| <span class="kw">use </span>std::usize; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::registry::{Registry, WorkerThread}; |
| |
| <span class="doccomment">/// We define various kinds of latches, which are all a primitive signaling |
| /// mechanism. A latch starts as false. Eventually someone calls `set()` and |
| /// it becomes true. You can test if it has been set by calling `probe()`. |
| /// |
| /// Some kinds of latches, but not all, support a `wait()` operation |
| /// that will wait until the latch is set, blocking efficiently. That |
| /// is not part of the trait since it is not possibly to do with all |
| /// latches. |
| /// |
| /// The intention is that `set()` is called once, but `probe()` may be |
| /// called any number of times. Once `probe()` returns true, the memory |
| /// effects that occurred before `set()` become visible. |
| /// |
| /// It'd probably be better to refactor the API into two paired types, |
| /// but that's a bit of work, and this is not a public API. |
| /// |
| /// ## Memory ordering |
| /// |
| /// Latches need to guarantee two things: |
| /// |
| /// - Once `probe()` returns true, all memory effects from the `set()` |
| /// are visible (in other words, the set should synchronize-with |
| /// the probe). |
| /// - Once `set()` occurs, the next `probe()` *will* observe it. This |
| /// typically requires a seq-cst ordering. See [the "tickle-then-get-sleepy" scenario in the sleep |
| /// README](/src/sleep/README.md#tickle-then-get-sleepy) for details. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">trait </span>Latch { |
| <span class="doccomment">/// Set the latch, signalling others. |
| /// |
| /// # WARNING |
| /// |
| /// Setting a latch triggers other threads to wake up and (in some |
| /// cases) complete. This may, in turn, cause memory to be |
| /// deallocated and so forth. One must be very careful about this, |
| /// and it's typically better to read all the fields you will need |
| /// to access *before* a latch is set! |
| /// |
| /// This function operates on `*const Self` instead of `&self` to allow it |
| /// to become dangling during this call. The caller must ensure that the |
| /// pointer is valid upon entry, and not invalidated during the call by any |
| /// actions other than `set` itself. |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>); |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">trait </span>AsCoreLatch { |
| <span class="kw">fn </span>as_core_latch(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>CoreLatch; |
| } |
| |
| <span class="doccomment">/// Latch is not set, owning thread is awake |
| </span><span class="kw">const </span>UNSET: usize = <span class="number">0</span>; |
| |
| <span class="doccomment">/// Latch is not set, owning thread is going to sleep on this latch |
| /// (but has not yet fallen asleep). |
| </span><span class="kw">const </span>SLEEPY: usize = <span class="number">1</span>; |
| |
| <span class="doccomment">/// Latch is not set, owning thread is asleep on this latch and |
| /// must be awoken. |
| </span><span class="kw">const </span>SLEEPING: usize = <span class="number">2</span>; |
| |
| <span class="doccomment">/// Latch is set. |
| </span><span class="kw">const </span>SET: usize = <span class="number">3</span>; |
| |
| <span class="doccomment">/// Spin latches are the simplest, most efficient kind, but they do |
| /// not support a `wait()` operation. They just have a boolean flag |
| /// that becomes true when `set()` is called. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>CoreLatch { |
| state: AtomicUsize, |
| } |
| |
| <span class="kw">impl </span>CoreLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| state: AtomicUsize::new(<span class="number">0</span>), |
| } |
| } |
| |
| <span class="doccomment">/// Returns the address of this core latch as an integer. Used |
| /// for logging. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>addr(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self </span><span class="kw">as </span><span class="kw-2">*const </span>CoreLatch <span class="kw">as </span>usize |
| } |
| |
| <span class="doccomment">/// Invoked by owning thread as it prepares to sleep. Returns true |
| /// if the owning thread may proceed to fall asleep, false if the |
| /// latch was set in the meantime. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>get_sleepy(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.state |
| .compare_exchange(UNSET, SLEEPY, Ordering::SeqCst, Ordering::Relaxed) |
| .is_ok() |
| } |
| |
| <span class="doccomment">/// Invoked by owning thread as it falls asleep sleep. Returns |
| /// true if the owning thread should block, or false if the latch |
| /// was set in the meantime. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>fall_asleep(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.state |
| .compare_exchange(SLEEPY, SLEEPING, Ordering::SeqCst, Ordering::Relaxed) |
| .is_ok() |
| } |
| |
| <span class="doccomment">/// Invoked by owning thread as it falls asleep sleep. Returns |
| /// true if the owning thread should block, or false if the latch |
| /// was set in the meantime. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>wake_up(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">if </span>!<span class="self">self</span>.probe() { |
| <span class="kw">let _ </span>= |
| <span class="self">self</span>.state |
| .compare_exchange(SLEEPING, UNSET, Ordering::SeqCst, Ordering::Relaxed); |
| } |
| } |
| |
| <span class="doccomment">/// Set the latch. If this returns true, the owning thread was sleeping |
| /// and must be awoken. |
| /// |
| /// This is private because, typically, setting a latch involves |
| /// doing some wakeups; those are encapsulated in the surrounding |
| /// latch code. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) -> bool { |
| <span class="kw">let </span>old_state = (<span class="kw-2">*</span>this).state.swap(SET, Ordering::AcqRel); |
| old_state == SLEEPING |
| } |
| |
| <span class="doccomment">/// Test if this latch has been set. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>probe(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.state.load(Ordering::Acquire) == SET |
| } |
| } |
| |
| <span class="doccomment">/// Spin latches are the simplest, most efficient kind, but they do |
| /// not support a `wait()` operation. They just have a boolean flag |
| /// that becomes true when `set()` is called. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>SpinLatch<<span class="lifetime">'r</span>> { |
| core_latch: CoreLatch, |
| registry: <span class="kw-2">&</span><span class="lifetime">'r </span>Arc<Registry>, |
| target_worker_index: usize, |
| cross: bool, |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'r</span>> SpinLatch<<span class="lifetime">'r</span>> { |
| <span class="doccomment">/// Creates a new spin latch that is owned by `thread`. This means |
| /// that `thread` is the only thread that should be blocking on |
| /// this latch -- it also means that when the latch is set, we |
| /// will wake `thread` if it is sleeping. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new(thread: <span class="kw-2">&</span><span class="lifetime">'r </span>WorkerThread) -> SpinLatch<<span class="lifetime">'r</span>> { |
| SpinLatch { |
| core_latch: CoreLatch::new(), |
| registry: thread.registry(), |
| target_worker_index: thread.index(), |
| cross: <span class="bool-val">false</span>, |
| } |
| } |
| |
| <span class="doccomment">/// Creates a new spin latch for cross-threadpool blocking. Notably, we |
| /// need to make sure the registry is kept alive after setting, so we can |
| /// safely call the notification. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>cross(thread: <span class="kw-2">&</span><span class="lifetime">'r </span>WorkerThread) -> SpinLatch<<span class="lifetime">'r</span>> { |
| SpinLatch { |
| cross: <span class="bool-val">true</span>, |
| ..SpinLatch::new(thread) |
| } |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>probe(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.core_latch.probe() |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'r</span>> AsCoreLatch <span class="kw">for </span>SpinLatch<<span class="lifetime">'r</span>> { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>as_core_latch(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>CoreLatch { |
| <span class="kw-2">&</span><span class="self">self</span>.core_latch |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'r</span>> Latch <span class="kw">for </span>SpinLatch<<span class="lifetime">'r</span>> { |
| <span class="attribute">#[inline] |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) { |
| <span class="kw">let </span>cross_registry; |
| |
| <span class="kw">let </span>registry: <span class="kw-2">&</span>Registry = <span class="kw">if </span>(<span class="kw-2">*</span>this).cross { |
| <span class="comment">// Ensure the registry stays alive while we notify it. |
| // Otherwise, it would be possible that we set the spin |
| // latch and the other thread sees it and exits, causing |
| // the registry to be deallocated, all before we get a |
| // chance to invoke `registry.notify_worker_latch_is_set`. |
| </span>cross_registry = Arc::clone((<span class="kw-2">*</span>this).registry); |
| <span class="kw-2">&</span>cross_registry |
| } <span class="kw">else </span>{ |
| <span class="comment">// If this is not a "cross-registry" spin-latch, then the |
| // thread which is performing `set` is itself ensuring |
| // that the registry stays alive. However, that doesn't |
| // include this *particular* `Arc` handle if the waiting |
| // thread then exits, so we must completely dereference it. |
| </span>(<span class="kw-2">*</span>this).registry |
| }; |
| <span class="kw">let </span>target_worker_index = (<span class="kw-2">*</span>this).target_worker_index; |
| |
| <span class="comment">// NOTE: Once we `set`, the target may proceed and invalidate `this`! |
| </span><span class="kw">if </span>CoreLatch::set(<span class="kw-2">&</span>(<span class="kw-2">*</span>this).core_latch) { |
| <span class="comment">// Subtle: at this point, we can no longer read from |
| // `self`, because the thread owning this spin latch may |
| // have awoken and deallocated the latch. Therefore, we |
| // only use fields whose values we already read. |
| </span>registry.notify_worker_latch_is_set(target_worker_index); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// A Latch starts as false and eventually becomes true. You can block |
| /// until it becomes true. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>LockLatch { |
| m: Mutex<bool>, |
| v: Condvar, |
| } |
| |
| <span class="kw">impl </span>LockLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -> LockLatch { |
| LockLatch { |
| m: Mutex::new(<span class="bool-val">false</span>), |
| v: Condvar::new(), |
| } |
| } |
| |
| <span class="doccomment">/// Block until latch is set, then resets this lock latch so it can be reused again. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>wait_and_reset(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">let </span><span class="kw-2">mut </span>guard = <span class="self">self</span>.m.lock().unwrap(); |
| <span class="kw">while </span>!<span class="kw-2">*</span>guard { |
| guard = <span class="self">self</span>.v.wait(guard).unwrap(); |
| } |
| <span class="kw-2">*</span>guard = <span class="bool-val">false</span>; |
| } |
| |
| <span class="doccomment">/// Block until latch is set. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>wait(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">let </span><span class="kw-2">mut </span>guard = <span class="self">self</span>.m.lock().unwrap(); |
| <span class="kw">while </span>!<span class="kw-2">*</span>guard { |
| guard = <span class="self">self</span>.v.wait(guard).unwrap(); |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Latch <span class="kw">for </span>LockLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) { |
| <span class="kw">let </span><span class="kw-2">mut </span>guard = (<span class="kw-2">*</span>this).m.lock().unwrap(); |
| <span class="kw-2">*</span>guard = <span class="bool-val">true</span>; |
| (<span class="kw-2">*</span>this).v.notify_all(); |
| } |
| } |
| |
| <span class="doccomment">/// Counting latches are used to implement scopes. They track a |
| /// counter. Unlike other latches, calling `set()` does not |
| /// necessarily make the latch be considered `set()`; instead, it just |
| /// decrements the counter. The latch is only "set" (in the sense that |
| /// `probe()` returns true) once the counter reaches zero. |
| /// |
| /// Note: like a `SpinLatch`, count laches are always associated with |
| /// some registry that is probing them, which must be tickled when |
| /// they are set. *Unlike* a `SpinLatch`, they don't themselves hold a |
| /// reference to that registry. This is because in some cases the |
| /// registry owns the count-latch, and that would create a cycle. So a |
| /// `CountLatch` must be given a reference to its owning registry when |
| /// it is set. For this reason, it does not implement the `Latch` |
| /// trait (but it doesn't have to, as it is not used in those generic |
| /// contexts). |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>CountLatch { |
| core_latch: CoreLatch, |
| counter: AtomicUsize, |
| } |
| |
| <span class="kw">impl </span>CountLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -> CountLatch { |
| <span class="self">Self</span>::with_count(<span class="number">1</span>) |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>with_count(n: usize) -> CountLatch { |
| CountLatch { |
| core_latch: CoreLatch::new(), |
| counter: AtomicUsize::new(n), |
| } |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>increment(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="macro">debug_assert!</span>(!<span class="self">self</span>.core_latch.probe()); |
| <span class="self">self</span>.counter.fetch_add(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| |
| <span class="doccomment">/// Decrements the latch counter by one. If this is the final |
| /// count, then the latch is **set**, and calls to `probe()` will |
| /// return true. Returns whether the latch was set. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) -> bool { |
| <span class="kw">if </span>(<span class="kw-2">*</span>this).counter.fetch_sub(<span class="number">1</span>, Ordering::SeqCst) == <span class="number">1 </span>{ |
| CoreLatch::set(<span class="kw-2">&</span>(<span class="kw-2">*</span>this).core_latch); |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>} |
| } |
| |
| <span class="doccomment">/// Decrements the latch counter by one and possibly set it. If |
| /// the latch is set, then the specific worker thread is tickled, |
| /// which should be the one that owns this latch. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">unsafe fn </span>set_and_tickle_one( |
| this: <span class="kw-2">*const </span><span class="self">Self</span>, |
| registry: <span class="kw-2">&</span>Registry, |
| target_worker_index: usize, |
| ) { |
| <span class="kw">if </span><span class="self">Self</span>::set(this) { |
| registry.notify_worker_latch_is_set(target_worker_index); |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>AsCoreLatch <span class="kw">for </span>CountLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">fn </span>as_core_latch(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>CoreLatch { |
| <span class="kw-2">&</span><span class="self">self</span>.core_latch |
| } |
| } |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>CountLockLatch { |
| lock_latch: LockLatch, |
| counter: AtomicUsize, |
| } |
| |
| <span class="kw">impl </span>CountLockLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>with_count(n: usize) -> CountLockLatch { |
| CountLockLatch { |
| lock_latch: LockLatch::new(), |
| counter: AtomicUsize::new(n), |
| } |
| } |
| |
| <span class="attribute">#[inline] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>increment(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">let </span>old_counter = <span class="self">self</span>.counter.fetch_add(<span class="number">1</span>, Ordering::Relaxed); |
| <span class="macro">debug_assert!</span>(old_counter != <span class="number">0</span>); |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>wait(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.lock_latch.wait(); |
| } |
| } |
| |
| <span class="kw">impl </span>Latch <span class="kw">for </span>CountLockLatch { |
| <span class="attribute">#[inline] |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) { |
| <span class="kw">if </span>(<span class="kw-2">*</span>this).counter.fetch_sub(<span class="number">1</span>, Ordering::SeqCst) == <span class="number">1 </span>{ |
| LockLatch::set(<span class="kw-2">&</span>(<span class="kw-2">*</span>this).lock_latch); |
| } |
| } |
| } |
| |
| <span class="doccomment">/// `&L` without any implication of `dereferenceable` for `Latch::set` |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>LatchRef<<span class="lifetime">'a</span>, L> { |
| inner: <span class="kw-2">*const </span>L, |
| marker: PhantomData<<span class="kw-2">&</span><span class="lifetime">'a </span>L>, |
| } |
| |
| <span class="kw">impl</span><L> LatchRef<<span class="lifetime">'_</span>, L> { |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new(inner: <span class="kw-2">&</span>L) -> LatchRef<<span class="lifetime">'_</span>, L> { |
| LatchRef { |
| inner, |
| marker: PhantomData, |
| } |
| } |
| } |
| |
| <span class="kw">unsafe impl</span><L: Sync> Sync <span class="kw">for </span>LatchRef<<span class="lifetime">'_</span>, L> {} |
| |
| <span class="kw">impl</span><L> Deref <span class="kw">for </span>LatchRef<<span class="lifetime">'_</span>, L> { |
| <span class="kw">type </span>Target = L; |
| |
| <span class="kw">fn </span>deref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>L { |
| <span class="comment">// SAFETY: if we have &self, the inner latch is still alive |
| </span><span class="kw">unsafe </span>{ <span class="kw-2">&*</span><span class="self">self</span>.inner } |
| } |
| } |
| |
| <span class="kw">impl</span><L: Latch> Latch <span class="kw">for </span>LatchRef<<span class="lifetime">'_</span>, L> { |
| <span class="attribute">#[inline] |
| </span><span class="kw">unsafe fn </span>set(this: <span class="kw-2">*const </span><span class="self">Self</span>) { |
| L::set((<span class="kw-2">*</span>this).inner); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="rayon_core" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
