| <!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/tokio-377c595163f99a10/dfe252d/tokio/src/runtime/scheduler/multi_thread/park.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>park.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="../../../../../tokio/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="../../../../../tokio/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> |
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| </pre><pre class="rust"><code><span class="doccomment">//! Parks the runtime. |
| //! |
| //! A combination of the various resource driver park handles. |
| |
| </span><span class="kw">use </span><span class="kw">crate</span>::loom::sync::atomic::AtomicUsize; |
| <span class="kw">use </span><span class="kw">crate</span>::loom::sync::{Arc, Condvar, Mutex}; |
| <span class="kw">use </span><span class="kw">crate</span>::loom::thread; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::driver::{<span class="self">self</span>, Driver}; |
| <span class="kw">use </span><span class="kw">crate</span>::util::TryLock; |
| |
| <span class="kw">use </span>std::sync::atomic::Ordering::SeqCst; |
| <span class="kw">use </span>std::time::Duration; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Parker { |
| inner: Arc<Inner>, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Unparker { |
| inner: Arc<Inner>, |
| } |
| |
| <span class="kw">struct </span>Inner { |
| <span class="doccomment">/// Avoids entering the park if possible |
| </span>state: AtomicUsize, |
| |
| <span class="doccomment">/// Used to coordinate access to the driver / condvar |
| </span>mutex: Mutex<()>, |
| |
| <span class="doccomment">/// Condvar to block on if the driver is unavailable. |
| </span>condvar: Condvar, |
| |
| <span class="doccomment">/// Resource (I/O, time, ...) driver |
| </span>shared: Arc<Shared>, |
| } |
| |
| <span class="kw">const </span>EMPTY: usize = <span class="number">0</span>; |
| <span class="kw">const </span>PARKED_CONDVAR: usize = <span class="number">1</span>; |
| <span class="kw">const </span>PARKED_DRIVER: usize = <span class="number">2</span>; |
| <span class="kw">const </span>NOTIFIED: usize = <span class="number">3</span>; |
| |
| <span class="doccomment">/// Shared across multiple Parker handles |
| </span><span class="kw">struct </span>Shared { |
| <span class="doccomment">/// Shared driver. Only one thread at a time can use this |
| </span>driver: TryLock<Driver>, |
| } |
| |
| <span class="kw">impl </span>Parker { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(driver: Driver) -> Parker { |
| Parker { |
| inner: Arc::new(Inner { |
| state: AtomicUsize::new(EMPTY), |
| mutex: Mutex::new(()), |
| condvar: Condvar::new(), |
| shared: Arc::new(Shared { |
| driver: TryLock::new(driver), |
| }), |
| }), |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>unpark(<span class="kw-2">&</span><span class="self">self</span>) -> Unparker { |
| Unparker { |
| inner: <span class="self">self</span>.inner.clone(), |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>park(<span class="kw-2">&mut </span><span class="self">self</span>, handle: <span class="kw-2">&</span>driver::Handle) { |
| <span class="self">self</span>.inner.park(handle); |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>park_timeout(<span class="kw-2">&mut </span><span class="self">self</span>, handle: <span class="kw-2">&</span>driver::Handle, duration: Duration) { |
| <span class="comment">// Only parking with zero is supported... |
| </span><span class="macro">assert_eq!</span>(duration, Duration::from_millis(<span class="number">0</span>)); |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>driver) = <span class="self">self</span>.inner.shared.driver.try_lock() { |
| driver.park_timeout(handle, duration) |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>shutdown(<span class="kw-2">&mut </span><span class="self">self</span>, handle: <span class="kw-2">&</span>driver::Handle) { |
| <span class="self">self</span>.inner.shutdown(handle); |
| } |
| } |
| |
| <span class="kw">impl </span>Clone <span class="kw">for </span>Parker { |
| <span class="kw">fn </span>clone(<span class="kw-2">&</span><span class="self">self</span>) -> Parker { |
| Parker { |
| inner: Arc::new(Inner { |
| state: AtomicUsize::new(EMPTY), |
| mutex: Mutex::new(()), |
| condvar: Condvar::new(), |
| shared: <span class="self">self</span>.inner.shared.clone(), |
| }), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Unparker { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>unpark(<span class="kw-2">&</span><span class="self">self</span>, driver: <span class="kw-2">&</span>driver::Handle) { |
| <span class="self">self</span>.inner.unpark(driver); |
| } |
| } |
| |
| <span class="kw">impl </span>Inner { |
| <span class="doccomment">/// Parks the current thread for at most `dur`. |
| </span><span class="kw">fn </span>park(<span class="kw-2">&</span><span class="self">self</span>, handle: <span class="kw-2">&</span>driver::Handle) { |
| <span class="kw">for _ in </span><span class="number">0</span>..<span class="number">3 </span>{ |
| <span class="comment">// If we were previously notified then we consume this notification and |
| // return quickly. |
| </span><span class="kw">if </span><span class="self">self |
| </span>.state |
| .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst) |
| .is_ok() |
| { |
| <span class="kw">return</span>; |
| } |
| |
| thread::yield_now(); |
| } |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>driver) = <span class="self">self</span>.shared.driver.try_lock() { |
| <span class="self">self</span>.park_driver(<span class="kw-2">&mut </span>driver, handle); |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.park_condvar(); |
| } |
| } |
| |
| <span class="kw">fn </span>park_condvar(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="comment">// Otherwise we need to coordinate going to sleep |
| </span><span class="kw">let </span><span class="kw-2">mut </span>m = <span class="self">self</span>.mutex.lock(); |
| |
| <span class="kw">match </span><span class="self">self |
| </span>.state |
| .compare_exchange(EMPTY, PARKED_CONDVAR, SeqCst, SeqCst) |
| { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => {} |
| <span class="prelude-val">Err</span>(NOTIFIED) => { |
| <span class="comment">// We must read here, even though we know it will be `NOTIFIED`. |
| // This is because `unpark` may have been called again since we read |
| // `NOTIFIED` in the `compare_exchange` above. We must perform an |
| // acquire operation that synchronizes with that `unpark` to observe |
| // any writes it made before the call to unpark. To do that we must |
| // read from the write it made to `state`. |
| </span><span class="kw">let </span>old = <span class="self">self</span>.state.swap(EMPTY, SeqCst); |
| <span class="macro">debug_assert_eq!</span>(old, NOTIFIED, <span class="string">"park state changed unexpectedly"</span>); |
| |
| <span class="kw">return</span>; |
| } |
| <span class="prelude-val">Err</span>(actual) => <span class="macro">panic!</span>(<span class="string">"inconsistent park state; actual = {}"</span>, actual), |
| } |
| |
| <span class="kw">loop </span>{ |
| m = <span class="self">self</span>.condvar.wait(m).unwrap(); |
| |
| <span class="kw">if </span><span class="self">self |
| </span>.state |
| .compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst) |
| .is_ok() |
| { |
| <span class="comment">// got a notification |
| </span><span class="kw">return</span>; |
| } |
| |
| <span class="comment">// spurious wakeup, go back to sleep |
| </span>} |
| } |
| |
| <span class="kw">fn </span>park_driver(<span class="kw-2">&</span><span class="self">self</span>, driver: <span class="kw-2">&mut </span>Driver, handle: <span class="kw-2">&</span>driver::Handle) { |
| <span class="kw">match </span><span class="self">self |
| </span>.state |
| .compare_exchange(EMPTY, PARKED_DRIVER, SeqCst, SeqCst) |
| { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => {} |
| <span class="prelude-val">Err</span>(NOTIFIED) => { |
| <span class="comment">// We must read here, even though we know it will be `NOTIFIED`. |
| // This is because `unpark` may have been called again since we read |
| // `NOTIFIED` in the `compare_exchange` above. We must perform an |
| // acquire operation that synchronizes with that `unpark` to observe |
| // any writes it made before the call to unpark. To do that we must |
| // read from the write it made to `state`. |
| </span><span class="kw">let </span>old = <span class="self">self</span>.state.swap(EMPTY, SeqCst); |
| <span class="macro">debug_assert_eq!</span>(old, NOTIFIED, <span class="string">"park state changed unexpectedly"</span>); |
| |
| <span class="kw">return</span>; |
| } |
| <span class="prelude-val">Err</span>(actual) => <span class="macro">panic!</span>(<span class="string">"inconsistent park state; actual = {}"</span>, actual), |
| } |
| |
| driver.park(handle); |
| |
| <span class="kw">match </span><span class="self">self</span>.state.swap(EMPTY, SeqCst) { |
| NOTIFIED => {} <span class="comment">// got a notification, hurray! |
| </span>PARKED_DRIVER => {} <span class="comment">// no notification, alas |
| </span>n => <span class="macro">panic!</span>(<span class="string">"inconsistent park_timeout state: {}"</span>, n), |
| } |
| } |
| |
| <span class="kw">fn </span>unpark(<span class="kw-2">&</span><span class="self">self</span>, driver: <span class="kw-2">&</span>driver::Handle) { |
| <span class="comment">// To ensure the unparked thread will observe any writes we made before |
| // this call, we must perform a release operation that `park` can |
| // synchronize with. To do that we must write `NOTIFIED` even if `state` |
| // is already `NOTIFIED`. That is why this must be a swap rather than a |
| // compare-and-swap that returns if it reads `NOTIFIED` on failure. |
| </span><span class="kw">match </span><span class="self">self</span>.state.swap(NOTIFIED, SeqCst) { |
| EMPTY => {} <span class="comment">// no one was waiting |
| </span>NOTIFIED => {} <span class="comment">// already unparked |
| </span>PARKED_CONDVAR => <span class="self">self</span>.unpark_condvar(), |
| PARKED_DRIVER => driver.unpark(), |
| actual => <span class="macro">panic!</span>(<span class="string">"inconsistent state in unpark; actual = {}"</span>, actual), |
| } |
| } |
| |
| <span class="kw">fn </span>unpark_condvar(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="comment">// There is a period between when the parked thread sets `state` to |
| // `PARKED` (or last checked `state` in the case of a spurious wake |
| // up) and when it actually waits on `cvar`. If we were to notify |
| // during this period it would be ignored and then when the parked |
| // thread went to sleep it would never wake up. Fortunately, it has |
| // `lock` locked at this stage so we can acquire `lock` to wait until |
| // it is ready to receive the notification. |
| // |
| // Releasing `lock` before the call to `notify_one` means that when the |
| // parked thread wakes it doesn't get woken only to have to wait for us |
| // to release `lock`. |
| </span>drop(<span class="self">self</span>.mutex.lock()); |
| |
| <span class="self">self</span>.condvar.notify_one() |
| } |
| |
| <span class="kw">fn </span>shutdown(<span class="kw-2">&</span><span class="self">self</span>, handle: <span class="kw-2">&</span>driver::Handle) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(<span class="kw-2">mut </span>driver) = <span class="self">self</span>.shared.driver.try_lock() { |
| driver.shutdown(handle); |
| } |
| |
| <span class="self">self</span>.condvar.notify_all(); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
