| <!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/tokio-1.28.2/src/runtime/task/join.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>join.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="kw">use </span><span class="kw">crate</span>::runtime::task::{Header, RawTask}; |
| |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::future::Future; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::panic::{RefUnwindSafe, UnwindSafe}; |
| <span class="kw">use </span>std::pin::Pin; |
| <span class="kw">use </span>std::task::{Context, Poll, Waker}; |
| |
| <span class="macro">cfg_rt! </span>{ |
| <span class="doccomment">/// An owned permission to join on a task (await its termination). |
| /// |
| /// This can be thought of as the equivalent of [`std::thread::JoinHandle`] |
| /// for a Tokio task rather than a thread. Note that the background task |
| /// associated with this `JoinHandle` started running immediately when you |
| /// called spawn, even if you have not yet awaited the `JoinHandle`. |
| /// |
| /// A `JoinHandle` *detaches* the associated task when it is dropped, which |
| /// means that there is no longer any handle to the task, and no way to `join` |
| /// on it. |
| /// |
| /// This `struct` is created by the [`task::spawn`] and [`task::spawn_blocking`] |
| /// functions. |
| /// |
| /// # Cancel safety |
| /// |
| /// The `&mut JoinHandle<T>` type is cancel safe. If it is used as the event |
| /// in a `tokio::select!` statement and some other branch completes first, |
| /// then it is guaranteed that the output of the task is not lost. |
| /// |
| /// If a `JoinHandle` is dropped, then the task continues running in the |
| /// background and its return value is lost. |
| /// |
| /// # Examples |
| /// |
| /// Creation from [`task::spawn`]: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// |
| /// # async fn doc() { |
| /// let join_handle: task::JoinHandle<_> = task::spawn(async { |
| /// // some work here |
| /// }); |
| /// # } |
| /// ``` |
| /// |
| /// Creation from [`task::spawn_blocking`]: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// |
| /// # async fn doc() { |
| /// let join_handle: task::JoinHandle<_> = task::spawn_blocking(|| { |
| /// // some blocking work here |
| /// }); |
| /// # } |
| /// ``` |
| /// |
| /// The generic parameter `T` in `JoinHandle<T>` is the return type of the spawned task. |
| /// If the return value is an i32, the join handle has type `JoinHandle<i32>`: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// |
| /// # async fn doc() { |
| /// let join_handle: task::JoinHandle<i32> = task::spawn(async { |
| /// 5 + 3 |
| /// }); |
| /// # } |
| /// |
| /// ``` |
| /// |
| /// If the task does not have a return value, the join handle has type `JoinHandle<()>`: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// |
| /// # async fn doc() { |
| /// let join_handle: task::JoinHandle<()> = task::spawn(async { |
| /// println!("I return nothing."); |
| /// }); |
| /// # } |
| /// ``` |
| /// |
| /// Note that `handle.await` doesn't give you the return type directly. It is wrapped in a |
| /// `Result` because panics in the spawned task are caught by Tokio. The `?` operator has |
| /// to be double chained to extract the returned value: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// use std::io; |
| /// |
| /// #[tokio::main] |
| /// async fn main() -> io::Result<()> { |
| /// let join_handle: task::JoinHandle<Result<i32, io::Error>> = tokio::spawn(async { |
| /// Ok(5 + 3) |
| /// }); |
| /// |
| /// let result = join_handle.await??; |
| /// assert_eq!(result, 8); |
| /// Ok(()) |
| /// } |
| /// ``` |
| /// |
| /// If the task panics, the error is a [`JoinError`] that contains the panic: |
| /// |
| /// ``` |
| /// use tokio::task; |
| /// use std::io; |
| /// use std::panic; |
| /// |
| /// #[tokio::main] |
| /// async fn main() -> io::Result<()> { |
| /// let join_handle: task::JoinHandle<Result<i32, io::Error>> = tokio::spawn(async { |
| /// panic!("boom"); |
| /// }); |
| /// |
| /// let err = join_handle.await.unwrap_err(); |
| /// assert!(err.is_panic()); |
| /// Ok(()) |
| /// } |
| /// |
| /// ``` |
| /// Child being detached and outliving its parent: |
| /// |
| /// ```no_run |
| /// use tokio::task; |
| /// use tokio::time; |
| /// use std::time::Duration; |
| /// |
| /// # #[tokio::main] async fn main() { |
| /// let original_task = task::spawn(async { |
| /// let _detached_task = task::spawn(async { |
| /// // Here we sleep to make sure that the first task returns before. |
| /// time::sleep(Duration::from_millis(10)).await; |
| /// // This will be called, even though the JoinHandle is dropped. |
| /// println!("♫ Still alive ♫"); |
| /// }); |
| /// }); |
| /// |
| /// original_task.await.expect("The task being joined has panicked"); |
| /// println!("Original task is joined."); |
| /// |
| /// // We make sure that the new task has time to run, before the main |
| /// // task returns. |
| /// |
| /// time::sleep(Duration::from_millis(1000)).await; |
| /// # } |
| /// ``` |
| /// |
| /// [`task::spawn`]: crate::task::spawn() |
| /// [`task::spawn_blocking`]: crate::task::spawn_blocking |
| /// [`std::thread::JoinHandle`]: std::thread::JoinHandle |
| /// [`JoinError`]: crate::task::JoinError |
| </span><span class="kw">pub struct </span>JoinHandle<T> { |
| raw: RawTask, |
| _p: PhantomData<T>, |
| } |
| } |
| |
| <span class="kw">unsafe impl</span><T: Send> Send <span class="kw">for </span>JoinHandle<T> {} |
| <span class="kw">unsafe impl</span><T: Send> Sync <span class="kw">for </span>JoinHandle<T> {} |
| |
| <span class="kw">impl</span><T> UnwindSafe <span class="kw">for </span>JoinHandle<T> {} |
| <span class="kw">impl</span><T> RefUnwindSafe <span class="kw">for </span>JoinHandle<T> {} |
| |
| <span class="kw">impl</span><T> JoinHandle<T> { |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new(raw: RawTask) -> JoinHandle<T> { |
| JoinHandle { |
| raw, |
| _p: PhantomData, |
| } |
| } |
| |
| <span class="doccomment">/// Abort the task associated with the handle. |
| /// |
| /// Awaiting a cancelled task might complete as usual if the task was |
| /// already completed at the time it was cancelled, but most likely it |
| /// will fail with a [cancelled] `JoinError`. |
| /// |
| /// ```rust |
| /// use tokio::time; |
| /// |
| /// # #[tokio::main(flavor = "current_thread", start_paused = true)] |
| /// # async fn main() { |
| /// let mut handles = Vec::new(); |
| /// |
| /// handles.push(tokio::spawn(async { |
| /// time::sleep(time::Duration::from_secs(10)).await; |
| /// true |
| /// })); |
| /// |
| /// handles.push(tokio::spawn(async { |
| /// time::sleep(time::Duration::from_secs(10)).await; |
| /// false |
| /// })); |
| /// |
| /// for handle in &handles { |
| /// handle.abort(); |
| /// } |
| /// |
| /// for handle in handles { |
| /// assert!(handle.await.unwrap_err().is_cancelled()); |
| /// } |
| /// # } |
| /// ``` |
| /// [cancelled]: method@super::error::JoinError::is_cancelled |
| </span><span class="kw">pub fn </span>abort(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.raw.remote_abort(); |
| } |
| |
| <span class="doccomment">/// Checks if the task associated with this `JoinHandle` has finished. |
| /// |
| /// Please note that this method can return `false` even if [`abort`] has been |
| /// called on the task. This is because the cancellation process may take |
| /// some time, and this method does not return `true` until it has |
| /// completed. |
| /// |
| /// ```rust |
| /// use tokio::time; |
| /// |
| /// # #[tokio::main(flavor = "current_thread", start_paused = true)] |
| /// # async fn main() { |
| /// let handle1 = tokio::spawn(async { |
| /// // do some stuff here |
| /// }); |
| /// let handle2 = tokio::spawn(async { |
| /// // do some other stuff here |
| /// time::sleep(time::Duration::from_secs(10)).await; |
| /// }); |
| /// // Wait for the task to finish |
| /// handle2.abort(); |
| /// time::sleep(time::Duration::from_secs(1)).await; |
| /// assert!(handle1.is_finished()); |
| /// assert!(handle2.is_finished()); |
| /// # } |
| /// ``` |
| /// [`abort`]: method@JoinHandle::abort |
| </span><span class="kw">pub fn </span>is_finished(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span>state = <span class="self">self</span>.raw.header().state.load(); |
| state.is_complete() |
| } |
| |
| <span class="doccomment">/// Set the waker that is notified when the task completes. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>set_join_waker(<span class="kw-2">&mut </span><span class="self">self</span>, waker: <span class="kw-2">&</span>Waker) { |
| <span class="kw">if </span><span class="self">self</span>.raw.try_set_join_waker(waker) { |
| <span class="comment">// In this case the task has already completed. We wake the waker immediately. |
| </span>waker.wake_by_ref(); |
| } |
| } |
| |
| <span class="doccomment">/// Returns a new `AbortHandle` that can be used to remotely abort this task. |
| /// |
| /// Awaiting a task cancelled by the `AbortHandle` might complete as usual if the task was |
| /// already completed at the time it was cancelled, but most likely it |
| /// will fail with a [cancelled] `JoinError`. |
| /// |
| /// ```rust |
| /// use tokio::{time, task}; |
| /// |
| /// # #[tokio::main(flavor = "current_thread", start_paused = true)] |
| /// # async fn main() { |
| /// let mut handles = Vec::new(); |
| /// |
| /// handles.push(tokio::spawn(async { |
| /// time::sleep(time::Duration::from_secs(10)).await; |
| /// true |
| /// })); |
| /// |
| /// handles.push(tokio::spawn(async { |
| /// time::sleep(time::Duration::from_secs(10)).await; |
| /// false |
| /// })); |
| /// |
| /// let abort_handles: Vec<task::AbortHandle> = handles.iter().map(|h| h.abort_handle()).collect(); |
| /// |
| /// for handle in abort_handles { |
| /// handle.abort(); |
| /// } |
| /// |
| /// for handle in handles { |
| /// assert!(handle.await.unwrap_err().is_cancelled()); |
| /// } |
| /// # } |
| /// ``` |
| /// [cancelled]: method@super::error::JoinError::is_cancelled |
| </span><span class="kw">pub fn </span>abort_handle(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw">super</span>::AbortHandle { |
| <span class="self">self</span>.raw.ref_inc(); |
| <span class="kw">super</span>::AbortHandle::new(<span class="self">self</span>.raw) |
| } |
| |
| <span class="doccomment">/// Returns a [task ID] that uniquely identifies this task relative to other |
| /// currently spawned tasks. |
| /// |
| /// **Note**: This is an [unstable API][unstable]. The public API of this type |
| /// may break in 1.x releases. See [the documentation on unstable |
| /// features][unstable] for details. |
| /// |
| /// [task ID]: crate::task::Id |
| /// [unstable]: crate#unstable-features |
| </span><span class="attribute">#[cfg(tokio_unstable)] |
| #[cfg_attr(docsrs, doc(cfg(tokio_unstable)))] |
| </span><span class="kw">pub fn </span>id(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw">super</span>::Id { |
| <span class="comment">// Safety: The header pointer is valid. |
| </span><span class="kw">unsafe </span>{ Header::get_id(<span class="self">self</span>.raw.header_ptr()) } |
| } |
| } |
| |
| <span class="kw">impl</span><T> Unpin <span class="kw">for </span>JoinHandle<T> {} |
| |
| <span class="kw">impl</span><T> Future <span class="kw">for </span>JoinHandle<T> { |
| <span class="kw">type </span>Output = <span class="kw">super</span>::Result<T>; |
| |
| <span class="kw">fn </span>poll(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="self">Self</span>::Output> { |
| <span class="kw">let </span><span class="kw-2">mut </span>ret = Poll::Pending; |
| |
| <span class="comment">// Keep track of task budget |
| </span><span class="kw">let </span>coop = <span class="macro">ready!</span>(<span class="kw">crate</span>::runtime::coop::poll_proceed(cx)); |
| |
| <span class="comment">// Try to read the task output. If the task is not yet complete, the |
| // waker is stored and is notified once the task does complete. |
| // |
| // The function must go via the vtable, which requires erasing generic |
| // types. To do this, the function "return" is placed on the stack |
| // **before** calling the function and is passed into the function using |
| // `*mut ()`. |
| // |
| // Safety: |
| // |
| // The type of `T` must match the task's output type. |
| </span><span class="kw">unsafe </span>{ |
| <span class="self">self</span>.raw |
| .try_read_output(<span class="kw-2">&mut </span>ret <span class="kw">as </span><span class="kw-2">*mut </span><span class="kw">_ as </span><span class="kw-2">*mut </span>(), cx.waker()); |
| } |
| |
| <span class="kw">if </span>ret.is_ready() { |
| coop.made_progress(); |
| } |
| |
| ret |
| } |
| } |
| |
| <span class="kw">impl</span><T> Drop <span class="kw">for </span>JoinHandle<T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">if </span><span class="self">self</span>.raw.state().drop_join_handle_fast().is_ok() { |
| <span class="kw">return</span>; |
| } |
| |
| <span class="self">self</span>.raw.drop_join_handle_slow(); |
| } |
| } |
| |
| <span class="kw">impl</span><T> fmt::Debug <span class="kw">for </span>JoinHandle<T> |
| <span class="kw">where |
| </span>T: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, fmt: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="comment">// Safety: The header pointer is valid. |
| </span><span class="kw">let </span>id_ptr = <span class="kw">unsafe </span>{ Header::get_id_ptr(<span class="self">self</span>.raw.header_ptr()) }; |
| <span class="kw">let </span>id = <span class="kw">unsafe </span>{ id_ptr.as_ref() }; |
| fmt.debug_struct(<span class="string">"JoinHandle"</span>).field(<span class="string">"id"</span>, id).finish() |
| } |
| } |
| </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> |
