| <!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/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="attribute">#![cfg_attr(not(feature = <span class="string">"full"</span>), allow(dead_code))] |
| |
| </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>std::sync::atomic::Ordering::SeqCst; |
| <span class="kw">use </span>std::time::Duration; |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>ParkThread { |
| inner: Arc<Inner>, |
| } |
| |
| <span class="doccomment">/// Unblocks a thread that was blocked by `ParkThread`. |
| </span><span class="attribute">#[derive(Clone, Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>UnparkThread { |
| inner: Arc<Inner>, |
| } |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>Inner { |
| state: AtomicUsize, |
| mutex: Mutex<()>, |
| condvar: Condvar, |
| } |
| |
| <span class="kw">const </span>EMPTY: usize = <span class="number">0</span>; |
| <span class="kw">const </span>PARKED: usize = <span class="number">1</span>; |
| <span class="kw">const </span>NOTIFIED: usize = <span class="number">2</span>; |
| |
| <span class="macro">tokio_thread_local! </span>{ |
| <span class="kw">static </span>CURRENT_PARKER: ParkThread = ParkThread::new(); |
| } |
| |
| <span class="comment">// Bit of a hack, but it is only for loom |
| </span><span class="attribute">#[cfg(loom)] |
| </span><span class="macro">tokio_thread_local! </span>{ |
| <span class="kw">static </span>CURRENT_THREAD_PARK_COUNT: AtomicUsize = AtomicUsize::new(<span class="number">0</span>); |
| } |
| |
| <span class="comment">// ==== impl ParkThread ==== |
| |
| </span><span class="kw">impl </span>ParkThread { |
| <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>{ |
| inner: Arc::new(Inner { |
| state: AtomicUsize::new(EMPTY), |
| mutex: Mutex::new(()), |
| condvar: Condvar::new(), |
| }), |
| } |
| } |
| |
| <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>) -> UnparkThread { |
| <span class="kw">let </span>inner = <span class="self">self</span>.inner.clone(); |
| UnparkThread { inner } |
| } |
| |
| <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>) { |
| <span class="attribute">#[cfg(loom)] |
| </span>CURRENT_THREAD_PARK_COUNT.with(|count| count.fetch_add(<span class="number">1</span>, SeqCst)); |
| <span class="self">self</span>.inner.park(); |
| } |
| |
| <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>, duration: Duration) { |
| <span class="attribute">#[cfg(loom)] |
| </span>CURRENT_THREAD_PARK_COUNT.with(|count| count.fetch_add(<span class="number">1</span>, SeqCst)); |
| |
| <span class="comment">// Wasm doesn't have threads, so just sleep. |
| </span><span class="attribute">#[cfg(not(tokio_wasm))] |
| </span><span class="self">self</span>.inner.park_timeout(duration); |
| <span class="attribute">#[cfg(tokio_wasm)] |
| </span>std::thread::sleep(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>) { |
| <span class="self">self</span>.inner.shutdown(); |
| } |
| } |
| |
| <span class="comment">// ==== impl Inner ==== |
| |
| </span><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>) { |
| <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>; |
| } |
| |
| <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, 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_timeout(<span class="kw-2">&</span><span class="self">self</span>, dur: Duration) { |
| <span class="comment">// Like `park` above we have a fast path for an already-notified thread, |
| // and afterwards we start coordinating for a sleep. 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>; |
| } |
| |
| <span class="kw">if </span>dur == Duration::from_millis(<span class="number">0</span>) { |
| <span class="kw">return</span>; |
| } |
| |
| <span class="kw">let </span>m = <span class="self">self</span>.mutex.lock(); |
| |
| <span class="kw">match </span><span class="self">self</span>.state.compare_exchange(EMPTY, PARKED, 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 again here, see `park`. |
| </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_timeout state; actual = {}"</span>, actual), |
| } |
| |
| <span class="comment">// Wait with a timeout, and if we spuriously wake up or otherwise wake up |
| // from a notification, we just want to unconditionally set the state back to |
| // empty, either consuming a notification or un-flagging ourselves as |
| // parked. |
| </span><span class="kw">let </span>(_m, _result) = <span class="self">self</span>.condvar.wait_timeout(m, dur).unwrap(); |
| |
| <span class="kw">match </span><span class="self">self</span>.state.swap(EMPTY, SeqCst) { |
| NOTIFIED => {} <span class="comment">// got a notification, hurray! |
| </span>PARKED => {} <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>) { |
| <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="kw">return</span>, <span class="comment">// no one was waiting |
| </span>NOTIFIED => <span class="kw">return</span>, <span class="comment">// already unparked |
| </span>PARKED => {} <span class="comment">// gotta go wake someone up |
| </span><span class="kw">_ </span>=> <span class="macro">panic!</span>(<span class="string">"inconsistent state in unpark"</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>) { |
| <span class="self">self</span>.condvar.notify_all(); |
| } |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>ParkThread { |
| <span class="kw">fn </span>default() -> <span class="self">Self </span>{ |
| <span class="self">Self</span>::new() |
| } |
| } |
| |
| <span class="comment">// ===== impl UnparkThread ===== |
| |
| </span><span class="kw">impl </span>UnparkThread { |
| <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>) { |
| <span class="self">self</span>.inner.unpark(); |
| } |
| } |
| |
| <span class="kw">use </span><span class="kw">crate</span>::loom::thread::AccessError; |
| <span class="kw">use </span>std::future::Future; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::mem; |
| <span class="kw">use </span>std::rc::Rc; |
| <span class="kw">use </span>std::task::{RawWaker, RawWakerVTable, Waker}; |
| |
| <span class="doccomment">/// Blocks the current thread using a condition variable. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>CachedParkThread { |
| _anchor: PhantomData<Rc<()>>, |
| } |
| |
| <span class="kw">impl </span>CachedParkThread { |
| <span class="doccomment">/// Creates a new `ParkThread` handle for the current thread. |
| /// |
| /// This type cannot be moved to other threads, so it should be created on |
| /// the thread that the caller intends to park. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new() -> CachedParkThread { |
| CachedParkThread { |
| _anchor: PhantomData, |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>waker(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><Waker, AccessError> { |
| <span class="self">self</span>.unpark().map(|unpark| unpark.into_waker()) |
| } |
| |
| <span class="kw">fn </span>unpark(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><UnparkThread, AccessError> { |
| <span class="self">self</span>.with_current(|park_thread| park_thread.unpark()) |
| } |
| |
| <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>) { |
| <span class="self">self</span>.with_current(|park_thread| park_thread.inner.park()) |
| .unwrap(); |
| } |
| |
| <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>, duration: Duration) { |
| <span class="self">self</span>.with_current(|park_thread| park_thread.inner.park_timeout(duration)) |
| .unwrap(); |
| } |
| |
| <span class="doccomment">/// Gets a reference to the `ParkThread` handle for this thread. |
| </span><span class="kw">fn </span>with_current<F, R>(<span class="kw-2">&</span><span class="self">self</span>, f: F) -> <span class="prelude-ty">Result</span><R, AccessError> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="kw-2">&</span>ParkThread) -> R, |
| { |
| CURRENT_PARKER.try_with(|inner| f(inner)) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>block_on<F: Future>(<span class="kw-2">&mut </span><span class="self">self</span>, f: F) -> <span class="prelude-ty">Result</span><F::Output, AccessError> { |
| <span class="kw">use </span>std::task::Context; |
| <span class="kw">use </span>std::task::Poll::Ready; |
| |
| <span class="comment">// `get_unpark()` should not return a Result |
| </span><span class="kw">let </span>waker = <span class="self">self</span>.waker()<span class="question-mark">?</span>; |
| <span class="kw">let </span><span class="kw-2">mut </span>cx = Context::from_waker(<span class="kw-2">&</span>waker); |
| |
| <span class="macro">pin!</span>(f); |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">if let </span>Ready(v) = <span class="kw">crate</span>::runtime::coop::budget(|| f.as_mut().poll(<span class="kw-2">&mut </span>cx)) { |
| <span class="kw">return </span><span class="prelude-val">Ok</span>(v); |
| } |
| |
| <span class="comment">// Wake any yielded tasks before parking in order to avoid |
| // blocking. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span><span class="kw">crate</span>::runtime::context::with_defer(|defer| defer.wake()); |
| |
| <span class="self">self</span>.park(); |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>UnparkThread { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>into_waker(<span class="self">self</span>) -> Waker { |
| <span class="kw">unsafe </span>{ |
| <span class="kw">let </span>raw = unparker_to_raw_waker(<span class="self">self</span>.inner); |
| Waker::from_raw(raw) |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Inner { |
| <span class="attribute">#[allow(clippy::wrong_self_convention)] |
| </span><span class="kw">fn </span>into_raw(this: Arc<Inner>) -> <span class="kw-2">*const </span>() { |
| Arc::into_raw(this) <span class="kw">as </span><span class="kw-2">*const </span>() |
| } |
| |
| <span class="kw">unsafe fn </span>from_raw(ptr: <span class="kw-2">*const </span>()) -> Arc<Inner> { |
| Arc::from_raw(ptr <span class="kw">as </span><span class="kw-2">*const </span>Inner) |
| } |
| } |
| |
| <span class="kw">unsafe fn </span>unparker_to_raw_waker(unparker: Arc<Inner>) -> RawWaker { |
| RawWaker::new( |
| Inner::into_raw(unparker), |
| <span class="kw-2">&</span>RawWakerVTable::new(clone, wake, wake_by_ref, drop_waker), |
| ) |
| } |
| |
| <span class="kw">unsafe fn </span>clone(raw: <span class="kw-2">*const </span>()) -> RawWaker { |
| <span class="kw">let </span>unparker = Inner::from_raw(raw); |
| |
| <span class="comment">// Increment the ref count |
| </span>mem::forget(unparker.clone()); |
| |
| unparker_to_raw_waker(unparker) |
| } |
| |
| <span class="kw">unsafe fn </span>drop_waker(raw: <span class="kw-2">*const </span>()) { |
| <span class="kw">let _ </span>= Inner::from_raw(raw); |
| } |
| |
| <span class="kw">unsafe fn </span>wake(raw: <span class="kw-2">*const </span>()) { |
| <span class="kw">let </span>unparker = Inner::from_raw(raw); |
| unparker.unpark(); |
| } |
| |
| <span class="kw">unsafe fn </span>wake_by_ref(raw: <span class="kw-2">*const </span>()) { |
| <span class="kw">let </span>unparker = Inner::from_raw(raw); |
| unparker.unpark(); |
| |
| <span class="comment">// We don't actually own a reference to the unparker |
| </span>mem::forget(unparker); |
| } |
| |
| <span class="attribute">#[cfg(loom)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>current_thread_park_count() -> usize { |
| CURRENT_THREAD_PARK_COUNT.with(|count| count.load(SeqCst)) |
| } |
| </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> |
