| <!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/registry/src/github.com-1ecc6299db9ec823/crossbeam-epoch-0.9.14/src/sync/list.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>list.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="../../../crossbeam_epoch/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="../../../crossbeam_epoch/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> |
| <span id="415">415</span> |
| <span id="416">416</span> |
| <span id="417">417</span> |
| <span id="418">418</span> |
| <span id="419">419</span> |
| <span id="420">420</span> |
| <span id="421">421</span> |
| <span id="422">422</span> |
| <span id="423">423</span> |
| <span id="424">424</span> |
| <span id="425">425</span> |
| <span id="426">426</span> |
| <span id="427">427</span> |
| <span id="428">428</span> |
| <span id="429">429</span> |
| <span id="430">430</span> |
| <span id="431">431</span> |
| <span id="432">432</span> |
| <span id="433">433</span> |
| <span id="434">434</span> |
| <span id="435">435</span> |
| <span id="436">436</span> |
| <span id="437">437</span> |
| <span id="438">438</span> |
| <span id="439">439</span> |
| <span id="440">440</span> |
| <span id="441">441</span> |
| <span id="442">442</span> |
| <span id="443">443</span> |
| <span id="444">444</span> |
| <span id="445">445</span> |
| <span id="446">446</span> |
| <span id="447">447</span> |
| <span id="448">448</span> |
| <span id="449">449</span> |
| <span id="450">450</span> |
| <span id="451">451</span> |
| <span id="452">452</span> |
| <span id="453">453</span> |
| <span id="454">454</span> |
| <span id="455">455</span> |
| <span id="456">456</span> |
| <span id="457">457</span> |
| <span id="458">458</span> |
| <span id="459">459</span> |
| <span id="460">460</span> |
| <span id="461">461</span> |
| <span id="462">462</span> |
| <span id="463">463</span> |
| <span id="464">464</span> |
| <span id="465">465</span> |
| <span id="466">466</span> |
| <span id="467">467</span> |
| <span id="468">468</span> |
| <span id="469">469</span> |
| <span id="470">470</span> |
| <span id="471">471</span> |
| <span id="472">472</span> |
| <span id="473">473</span> |
| <span id="474">474</span> |
| <span id="475">475</span> |
| <span id="476">476</span> |
| <span id="477">477</span> |
| <span id="478">478</span> |
| <span id="479">479</span> |
| <span id="480">480</span> |
| <span id="481">481</span> |
| <span id="482">482</span> |
| <span id="483">483</span> |
| <span id="484">484</span> |
| <span id="485">485</span> |
| <span id="486">486</span> |
| <span id="487">487</span> |
| </pre><pre class="rust"><code><span class="doccomment">//! Lock-free intrusive linked list. |
| //! |
| //! Ideas from Michael. High Performance Dynamic Lock-Free Hash Tables and List-Based Sets. SPAA |
| //! 2002. <http://dl.acm.org/citation.cfm?id=564870.564881> |
| |
| </span><span class="kw">use </span>core::marker::PhantomData; |
| <span class="kw">use </span>core::sync::atomic::Ordering::{Acquire, Relaxed, Release}; |
| |
| <span class="kw">use crate</span>::{unprotected, Atomic, Guard, Shared}; |
| |
| <span class="doccomment">/// An entry in a linked list. |
| /// |
| /// An Entry is accessed from multiple threads, so it would be beneficial to put it in a different |
| /// cache-line than thread-local data in terms of performance. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Entry { |
| <span class="doccomment">/// The next entry in the linked list. |
| /// If the tag is 1, this entry is marked as deleted. |
| </span>next: Atomic<Entry>, |
| } |
| |
| <span class="doccomment">/// Implementing this trait asserts that the type `T` can be used as an element in the intrusive |
| /// linked list defined in this module. `T` has to contain (or otherwise be linked to) an instance |
| /// of `Entry`. |
| /// |
| /// # Example |
| /// |
| /// ```ignore |
| /// struct A { |
| /// entry: Entry, |
| /// data: usize, |
| /// } |
| /// |
| /// impl IsElement<A> for A { |
| /// fn entry_of(a: &A) -> &Entry { |
| /// let entry_ptr = ((a as usize) + offset_of!(A, entry)) as *const Entry; |
| /// unsafe { &*entry_ptr } |
| /// } |
| /// |
| /// unsafe fn element_of(entry: &Entry) -> &T { |
| /// let elem_ptr = ((entry as usize) - offset_of!(A, entry)) as *const T; |
| /// &*elem_ptr |
| /// } |
| /// |
| /// unsafe fn finalize(entry: &Entry, guard: &Guard) { |
| /// guard.defer_destroy(Shared::from(Self::element_of(entry) as *const _)); |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// This trait is implemented on a type separate from `T` (although it can be just `T`), because |
| /// one type might be placeable into multiple lists, in which case it would require multiple |
| /// implementations of `IsElement`. In such cases, each struct implementing `IsElement<T>` |
| /// represents a distinct `Entry` in `T`. |
| /// |
| /// For example, we can insert the following struct into two lists using `entry1` for one |
| /// and `entry2` for the other: |
| /// |
| /// ```ignore |
| /// struct B { |
| /// entry1: Entry, |
| /// entry2: Entry, |
| /// data: usize, |
| /// } |
| /// ``` |
| /// |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">trait </span>IsElement<T> { |
| <span class="doccomment">/// Returns a reference to this element's `Entry`. |
| </span><span class="kw">fn </span>entry_of(<span class="kw">_</span>: <span class="kw-2">&</span>T) -> <span class="kw-2">&</span>Entry; |
| |
| <span class="doccomment">/// Given a reference to an element's entry, returns that element. |
| /// |
| /// ```ignore |
| /// let elem = ListElement::new(); |
| /// assert_eq!(elem.entry_of(), |
| /// unsafe { ListElement::element_of(elem.entry_of()) } ); |
| /// ``` |
| /// |
| /// # Safety |
| /// |
| /// The caller has to guarantee that the `Entry` is called with was retrieved from an instance |
| /// of the element type (`T`). |
| </span><span class="kw">unsafe fn </span>element_of(<span class="kw">_</span>: <span class="kw-2">&</span>Entry) -> <span class="kw-2">&</span>T; |
| |
| <span class="doccomment">/// The function that is called when an entry is unlinked from list. |
| /// |
| /// # Safety |
| /// |
| /// The caller has to guarantee that the `Entry` is called with was retrieved from an instance |
| /// of the element type (`T`). |
| </span><span class="kw">unsafe fn </span>finalize(<span class="kw">_</span>: <span class="kw-2">&</span>Entry, <span class="kw">_</span>: <span class="kw-2">&</span>Guard); |
| } |
| |
| <span class="doccomment">/// A lock-free, intrusive linked list of type `T`. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>List<T, C: IsElement<T> = T> { |
| <span class="doccomment">/// The head of the linked list. |
| </span>head: Atomic<Entry>, |
| |
| <span class="doccomment">/// The phantom data for using `T` and `C`. |
| </span>_marker: PhantomData<(T, C)>, |
| } |
| |
| <span class="doccomment">/// An iterator used for retrieving values from the list. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Iter<<span class="lifetime">'g</span>, T, C: IsElement<T>> { |
| <span class="doccomment">/// The guard that protects the iteration. |
| </span>guard: <span class="kw-2">&</span><span class="lifetime">'g </span>Guard, |
| |
| <span class="doccomment">/// Pointer from the predecessor to the current entry. |
| </span>pred: <span class="kw-2">&</span><span class="lifetime">'g </span>Atomic<Entry>, |
| |
| <span class="doccomment">/// The current entry. |
| </span>curr: Shared<<span class="lifetime">'g</span>, Entry>, |
| |
| <span class="doccomment">/// The list head, needed for restarting iteration. |
| </span>head: <span class="kw-2">&</span><span class="lifetime">'g </span>Atomic<Entry>, |
| |
| <span class="doccomment">/// Logically, we store a borrow of an instance of `T` and |
| /// use the type information from `C`. |
| </span>_marker: PhantomData<(<span class="kw-2">&</span><span class="lifetime">'g </span>T, C)>, |
| } |
| |
| <span class="doccomment">/// An error that occurs during iteration over the list. |
| </span><span class="attribute">#[derive(PartialEq, Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>IterError { |
| <span class="doccomment">/// A concurrent thread modified the state of the list at the same place that this iterator |
| /// was inspecting. Subsequent iteration will restart from the beginning of the list. |
| </span>Stalled, |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>Entry { |
| <span class="doccomment">/// Returns the empty entry. |
| </span><span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| next: Atomic::null(), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Entry { |
| <span class="doccomment">/// Marks this entry as deleted, deferring the actual deallocation to a later iteration. |
| /// |
| /// # Safety |
| /// |
| /// The entry should be a member of a linked list, and it should not have been deleted. |
| /// It should be safe to call `C::finalize` on the entry after the `guard` is dropped, where `C` |
| /// is the associated helper for the linked list. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>delete(<span class="kw-2">&</span><span class="self">self</span>, guard: <span class="kw-2">&</span>Guard) { |
| <span class="self">self</span>.next.fetch_or(<span class="number">1</span>, Release, guard); |
| } |
| } |
| |
| <span class="kw">impl</span><T, C: IsElement<T>> List<T, C> { |
| <span class="doccomment">/// Returns a new, empty linked list. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new() -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| head: Atomic::null(), |
| _marker: PhantomData, |
| } |
| } |
| |
| <span class="doccomment">/// Inserts `entry` into the head of the list. |
| /// |
| /// # Safety |
| /// |
| /// You should guarantee that: |
| /// |
| /// - `container` is not null |
| /// - `container` is immovable, e.g. inside an `Owned` |
| /// - the same `Entry` is not inserted more than once |
| /// - the inserted object will be removed before the list is dropped |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>insert<<span class="lifetime">'g</span>>(<span class="kw-2">&</span><span class="lifetime">'g </span><span class="self">self</span>, container: Shared<<span class="lifetime">'g</span>, T>, guard: <span class="kw-2">&</span><span class="lifetime">'g </span>Guard) { |
| <span class="comment">// Insert right after head, i.e. at the beginning of the list. |
| </span><span class="kw">let </span>to = <span class="kw-2">&</span><span class="self">self</span>.head; |
| <span class="comment">// Get the intrusively stored Entry of the new element to insert. |
| </span><span class="kw">let </span>entry: <span class="kw-2">&</span>Entry = C::entry_of(container.deref()); |
| <span class="comment">// Make a Shared ptr to that Entry. |
| </span><span class="kw">let </span>entry_ptr = Shared::from(entry <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_</span>); |
| <span class="comment">// Read the current successor of where we want to insert. |
| </span><span class="kw">let </span><span class="kw-2">mut </span>next = to.load(Relaxed, guard); |
| |
| <span class="kw">loop </span>{ |
| <span class="comment">// Set the Entry of the to-be-inserted element to point to the previous successor of |
| // `to`. |
| </span>entry.next.store(next, Relaxed); |
| <span class="kw">match </span>to.compare_exchange_weak(next, entry_ptr, Release, Relaxed, guard) { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => <span class="kw">break</span>, |
| <span class="comment">// We lost the race or weak CAS failed spuriously. Update the successor and try |
| // again. |
| </span><span class="prelude-val">Err</span>(err) => next = err.current, |
| } |
| } |
| } |
| |
| <span class="doccomment">/// Returns an iterator over all objects. |
| /// |
| /// # Caveat |
| /// |
| /// Every object that is inserted at the moment this function is called and persists at least |
| /// until the end of iteration will be returned. Since this iterator traverses a lock-free |
| /// linked list that may be concurrently modified, some additional caveats apply: |
| /// |
| /// 1. If a new object is inserted during iteration, it may or may not be returned. |
| /// 2. If an object is deleted during iteration, it may or may not be returned. |
| /// 3. The iteration may be aborted when it lost in a race condition. In this case, the winning |
| /// thread will continue to iterate over the same list. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>iter<<span class="lifetime">'g</span>>(<span class="kw-2">&</span><span class="lifetime">'g </span><span class="self">self</span>, guard: <span class="kw-2">&</span><span class="lifetime">'g </span>Guard) -> Iter<<span class="lifetime">'g</span>, T, C> { |
| Iter { |
| guard, |
| pred: <span class="kw-2">&</span><span class="self">self</span>.head, |
| curr: <span class="self">self</span>.head.load(Acquire, guard), |
| head: <span class="kw-2">&</span><span class="self">self</span>.head, |
| _marker: PhantomData, |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T, C: IsElement<T>> Drop <span class="kw">for </span>List<T, C> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">unsafe </span>{ |
| <span class="kw">let </span>guard = unprotected(); |
| <span class="kw">let </span><span class="kw-2">mut </span>curr = <span class="self">self</span>.head.load(Relaxed, guard); |
| <span class="kw">while let </span><span class="prelude-val">Some</span>(c) = curr.as_ref() { |
| <span class="kw">let </span>succ = c.next.load(Relaxed, guard); |
| <span class="comment">// Verify that all elements have been removed from the list. |
| </span><span class="macro">assert_eq!</span>(succ.tag(), <span class="number">1</span>); |
| |
| C::finalize(curr.deref(), guard); |
| curr = succ; |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'g</span>, T: <span class="lifetime">'g</span>, C: IsElement<T>> Iterator <span class="kw">for </span>Iter<<span class="lifetime">'g</span>, T, C> { |
| <span class="kw">type </span>Item = <span class="prelude-ty">Result</span><<span class="kw-2">&</span><span class="lifetime">'g </span>T, IterError>; |
| |
| <span class="kw">fn </span>next(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><<span class="self">Self</span>::Item> { |
| <span class="kw">while let </span><span class="prelude-val">Some</span>(c) = <span class="kw">unsafe </span>{ <span class="self">self</span>.curr.as_ref() } { |
| <span class="kw">let </span>succ = c.next.load(Acquire, <span class="self">self</span>.guard); |
| |
| <span class="kw">if </span>succ.tag() == <span class="number">1 </span>{ |
| <span class="comment">// This entry was removed. Try unlinking it from the list. |
| </span><span class="kw">let </span>succ = succ.with_tag(<span class="number">0</span>); |
| |
| <span class="comment">// The tag should always be zero, because removing a node after a logically deleted |
| // node leaves the list in an invalid state. |
| </span><span class="macro">debug_assert!</span>(<span class="self">self</span>.curr.tag() == <span class="number">0</span>); |
| |
| <span class="comment">// Try to unlink `curr` from the list, and get the new value of `self.pred`. |
| </span><span class="kw">let </span>succ = <span class="kw">match </span><span class="self">self |
| </span>.pred |
| .compare_exchange(<span class="self">self</span>.curr, succ, Acquire, Acquire, <span class="self">self</span>.guard) |
| { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => { |
| <span class="comment">// We succeeded in unlinking `curr`, so we have to schedule |
| // deallocation. Deferred drop is okay, because `list.delete()` can only be |
| // called if `T: 'static`. |
| </span><span class="kw">unsafe </span>{ |
| C::finalize(<span class="self">self</span>.curr.deref(), <span class="self">self</span>.guard); |
| } |
| |
| <span class="comment">// `succ` is the new value of `self.pred`. |
| </span>succ |
| } |
| <span class="prelude-val">Err</span>(e) => { |
| <span class="comment">// `e.current` is the current value of `self.pred`. |
| </span>e.current |
| } |
| }; |
| |
| <span class="comment">// If the predecessor node is already marked as deleted, we need to restart from |
| // `head`. |
| </span><span class="kw">if </span>succ.tag() != <span class="number">0 </span>{ |
| <span class="self">self</span>.pred = <span class="self">self</span>.head; |
| <span class="self">self</span>.curr = <span class="self">self</span>.head.load(Acquire, <span class="self">self</span>.guard); |
| |
| <span class="kw">return </span><span class="prelude-val">Some</span>(<span class="prelude-val">Err</span>(IterError::Stalled)); |
| } |
| |
| <span class="comment">// Move over the removed by only advancing `curr`, not `pred`. |
| </span><span class="self">self</span>.curr = succ; |
| <span class="kw">continue</span>; |
| } |
| |
| <span class="comment">// Move one step forward. |
| </span><span class="self">self</span>.pred = <span class="kw-2">&</span>c.next; |
| <span class="self">self</span>.curr = succ; |
| |
| <span class="kw">return </span><span class="prelude-val">Some</span>(<span class="prelude-val">Ok</span>(<span class="kw">unsafe </span>{ C::element_of(c) })); |
| } |
| |
| <span class="comment">// We reached the end of the list. |
| </span><span class="prelude-val">None |
| </span>} |
| } |
| |
| <span class="attribute">#[cfg(all(test, not(crossbeam_loom)))] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use crate</span>::{Collector, Owned}; |
| <span class="kw">use </span>crossbeam_utils::thread; |
| <span class="kw">use </span>std::sync::Barrier; |
| |
| <span class="kw">impl </span>IsElement<Entry> <span class="kw">for </span>Entry { |
| <span class="kw">fn </span>entry_of(entry: <span class="kw-2">&</span>Entry) -> <span class="kw-2">&</span>Entry { |
| entry |
| } |
| |
| <span class="kw">unsafe fn </span>element_of(entry: <span class="kw-2">&</span>Entry) -> <span class="kw-2">&</span>Entry { |
| entry |
| } |
| |
| <span class="kw">unsafe fn </span>finalize(entry: <span class="kw-2">&</span>Entry, guard: <span class="kw-2">&</span>Guard) { |
| guard.defer_destroy(Shared::from(<span class="self">Self</span>::element_of(entry) <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_</span>)); |
| } |
| } |
| |
| <span class="doccomment">/// Checks whether the list retains inserted elements |
| /// and returns them in the correct order. |
| </span><span class="attribute">#[test] |
| </span><span class="kw">fn </span>insert() { |
| <span class="kw">let </span>collector = Collector::new(); |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard = handle.pin(); |
| |
| <span class="kw">let </span>l: List<Entry> = List::new(); |
| |
| <span class="kw">let </span>e1 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>e2 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>e3 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| |
| <span class="kw">unsafe </span>{ |
| l.insert(e1, <span class="kw-2">&</span>guard); |
| l.insert(e2, <span class="kw-2">&</span>guard); |
| l.insert(e3, <span class="kw-2">&</span>guard); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>maybe_e3 = iter.next(); |
| <span class="macro">assert!</span>(maybe_e3.is_some()); |
| <span class="macro">assert!</span>(maybe_e3.unwrap().unwrap() <span class="kw">as </span><span class="kw-2">*const </span>Entry == e3.as_raw()); |
| <span class="kw">let </span>maybe_e2 = iter.next(); |
| <span class="macro">assert!</span>(maybe_e2.is_some()); |
| <span class="macro">assert!</span>(maybe_e2.unwrap().unwrap() <span class="kw">as </span><span class="kw-2">*const </span>Entry == e2.as_raw()); |
| <span class="kw">let </span>maybe_e1 = iter.next(); |
| <span class="macro">assert!</span>(maybe_e1.is_some()); |
| <span class="macro">assert!</span>(maybe_e1.unwrap().unwrap() <span class="kw">as </span><span class="kw-2">*const </span>Entry == e1.as_raw()); |
| <span class="macro">assert!</span>(iter.next().is_none()); |
| |
| <span class="kw">unsafe </span>{ |
| e1.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| e2.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| e3.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| } |
| } |
| |
| <span class="doccomment">/// Checks whether elements can be removed from the list and whether |
| /// the correct elements are removed. |
| </span><span class="attribute">#[test] |
| </span><span class="kw">fn </span>delete() { |
| <span class="kw">let </span>collector = Collector::new(); |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard = handle.pin(); |
| |
| <span class="kw">let </span>l: List<Entry> = List::new(); |
| |
| <span class="kw">let </span>e1 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>e2 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>e3 = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| <span class="kw">unsafe </span>{ |
| l.insert(e1, <span class="kw-2">&</span>guard); |
| l.insert(e2, <span class="kw-2">&</span>guard); |
| l.insert(e3, <span class="kw-2">&</span>guard); |
| e2.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="kw">let </span>maybe_e3 = iter.next(); |
| <span class="macro">assert!</span>(maybe_e3.is_some()); |
| <span class="macro">assert!</span>(maybe_e3.unwrap().unwrap() <span class="kw">as </span><span class="kw-2">*const </span>Entry == e3.as_raw()); |
| <span class="kw">let </span>maybe_e1 = iter.next(); |
| <span class="macro">assert!</span>(maybe_e1.is_some()); |
| <span class="macro">assert!</span>(maybe_e1.unwrap().unwrap() <span class="kw">as </span><span class="kw-2">*const </span>Entry == e1.as_raw()); |
| <span class="macro">assert!</span>(iter.next().is_none()); |
| |
| <span class="kw">unsafe </span>{ |
| e1.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| e3.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="macro">assert!</span>(iter.next().is_none()); |
| } |
| |
| <span class="kw">const </span>THREADS: usize = <span class="number">8</span>; |
| <span class="kw">const </span>ITERS: usize = <span class="number">512</span>; |
| |
| <span class="doccomment">/// Contends the list on insert and delete operations to make sure they can run concurrently. |
| </span><span class="attribute">#[test] |
| </span><span class="kw">fn </span>insert_delete_multi() { |
| <span class="kw">let </span>collector = Collector::new(); |
| |
| <span class="kw">let </span>l: List<Entry> = List::new(); |
| <span class="kw">let </span>b = Barrier::new(THREADS); |
| |
| thread::scope(|s| { |
| <span class="kw">for _ in </span><span class="number">0</span>..THREADS { |
| s.spawn(|<span class="kw">_</span>| { |
| b.wait(); |
| |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard: Guard = handle.pin(); |
| <span class="kw">let </span><span class="kw-2">mut </span>v = Vec::with_capacity(ITERS); |
| |
| <span class="kw">for _ in </span><span class="number">0</span>..ITERS { |
| <span class="kw">let </span>e = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| v.push(e); |
| <span class="kw">unsafe </span>{ |
| l.insert(e, <span class="kw-2">&</span>guard); |
| } |
| } |
| |
| <span class="kw">for </span>e <span class="kw">in </span>v { |
| <span class="kw">unsafe </span>{ |
| e.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| } |
| } |
| }); |
| } |
| }) |
| .unwrap(); |
| |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard = handle.pin(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="macro">assert!</span>(iter.next().is_none()); |
| } |
| |
| <span class="doccomment">/// Contends the list on iteration to make sure that it can be iterated over concurrently. |
| </span><span class="attribute">#[test] |
| </span><span class="kw">fn </span>iter_multi() { |
| <span class="kw">let </span>collector = Collector::new(); |
| |
| <span class="kw">let </span>l: List<Entry> = List::new(); |
| <span class="kw">let </span>b = Barrier::new(THREADS); |
| |
| thread::scope(|s| { |
| <span class="kw">for _ in </span><span class="number">0</span>..THREADS { |
| s.spawn(|<span class="kw">_</span>| { |
| b.wait(); |
| |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard: Guard = handle.pin(); |
| <span class="kw">let </span><span class="kw-2">mut </span>v = Vec::with_capacity(ITERS); |
| |
| <span class="kw">for _ in </span><span class="number">0</span>..ITERS { |
| <span class="kw">let </span>e = Owned::new(Entry::default()).into_shared(<span class="kw-2">&</span>guard); |
| v.push(e); |
| <span class="kw">unsafe </span>{ |
| l.insert(e, <span class="kw-2">&</span>guard); |
| } |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="kw">for _ in </span><span class="number">0</span>..ITERS { |
| <span class="macro">assert!</span>(iter.next().is_some()); |
| } |
| |
| <span class="kw">for </span>e <span class="kw">in </span>v { |
| <span class="kw">unsafe </span>{ |
| e.as_ref().unwrap().delete(<span class="kw-2">&</span>guard); |
| } |
| } |
| }); |
| } |
| }) |
| .unwrap(); |
| |
| <span class="kw">let </span>handle = collector.register(); |
| <span class="kw">let </span>guard = handle.pin(); |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>iter = l.iter(<span class="kw-2">&</span>guard); |
| <span class="macro">assert!</span>(iter.next().is_none()); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="crossbeam_epoch" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |