| <!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/blocking/pool.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>pool.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">//! Thread pool for blocking operations |
| |
| </span><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::blocking::schedule::BlockingSchedule; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::blocking::{shutdown, BlockingTask}; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::builder::ThreadNameFn; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::task::{<span class="self">self</span>, JoinHandle}; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::{Builder, Callback, Handle}; |
| |
| <span class="kw">use </span>std::collections::{HashMap, VecDeque}; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::io; |
| <span class="kw">use </span>std::sync::atomic::{AtomicUsize, Ordering}; |
| <span class="kw">use </span>std::time::Duration; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>BlockingPool { |
| spawner: Spawner, |
| shutdown_rx: shutdown::Receiver, |
| } |
| |
| <span class="attribute">#[derive(Clone)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Spawner { |
| inner: Arc<Inner>, |
| } |
| |
| <span class="attribute">#[derive(Default)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>SpawnerMetrics { |
| num_threads: AtomicUsize, |
| num_idle_threads: AtomicUsize, |
| queue_depth: AtomicUsize, |
| } |
| |
| <span class="kw">impl </span>SpawnerMetrics { |
| <span class="kw">fn </span>num_threads(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.num_threads.load(Ordering::Relaxed) |
| } |
| |
| <span class="kw">fn </span>num_idle_threads(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.num_idle_threads.load(Ordering::Relaxed) |
| } |
| |
| <span class="macro">cfg_metrics! </span>{ |
| <span class="kw">fn </span>queue_depth(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.queue_depth.load(Ordering::Relaxed) |
| } |
| } |
| |
| <span class="kw">fn </span>inc_num_threads(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.num_threads.fetch_add(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| |
| <span class="kw">fn </span>dec_num_threads(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.num_threads.fetch_sub(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| |
| <span class="kw">fn </span>inc_num_idle_threads(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.num_idle_threads.fetch_add(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| |
| <span class="kw">fn </span>dec_num_idle_threads(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.num_idle_threads.fetch_sub(<span class="number">1</span>, Ordering::Relaxed) |
| } |
| |
| <span class="kw">fn </span>inc_queue_depth(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.queue_depth.fetch_add(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| |
| <span class="kw">fn </span>dec_queue_depth(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="self">self</span>.queue_depth.fetch_sub(<span class="number">1</span>, Ordering::Relaxed); |
| } |
| } |
| |
| <span class="kw">struct </span>Inner { |
| <span class="doccomment">/// State shared between worker threads. |
| </span>shared: Mutex<Shared>, |
| |
| <span class="doccomment">/// Pool threads wait on this. |
| </span>condvar: Condvar, |
| |
| <span class="doccomment">/// Spawned threads use this name. |
| </span>thread_name: ThreadNameFn, |
| |
| <span class="doccomment">/// Spawned thread stack size. |
| </span>stack_size: <span class="prelude-ty">Option</span><usize>, |
| |
| <span class="doccomment">/// Call after a thread starts. |
| </span>after_start: <span class="prelude-ty">Option</span><Callback>, |
| |
| <span class="doccomment">/// Call before a thread stops. |
| </span>before_stop: <span class="prelude-ty">Option</span><Callback>, |
| |
| <span class="comment">// Maximum number of threads. |
| </span>thread_cap: usize, |
| |
| <span class="comment">// Customizable wait timeout. |
| </span>keep_alive: Duration, |
| |
| <span class="comment">// Metrics about the pool. |
| </span>metrics: SpawnerMetrics, |
| } |
| |
| <span class="kw">struct </span>Shared { |
| queue: VecDeque<Task>, |
| num_notify: u32, |
| shutdown: bool, |
| shutdown_tx: <span class="prelude-ty">Option</span><shutdown::Sender>, |
| <span class="doccomment">/// Prior to shutdown, we clean up JoinHandles by having each timed-out |
| /// thread join on the previous timed-out thread. This is not strictly |
| /// necessary but helps avoid Valgrind false positives, see |
| /// <https://github.com/tokio-rs/tokio/commit/646fbae76535e397ef79dbcaacb945d4c829f666> |
| /// for more information. |
| </span>last_exiting_thread: <span class="prelude-ty">Option</span><thread::JoinHandle<()>>, |
| <span class="doccomment">/// This holds the JoinHandles for all running threads; on shutdown, the thread |
| /// calling shutdown handles joining on these. |
| </span>worker_threads: HashMap<usize, thread::JoinHandle<()>>, |
| <span class="doccomment">/// This is a counter used to iterate worker_threads in a consistent order (for loom's |
| /// benefit). |
| </span>worker_thread_index: usize, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Task { |
| task: task::UnownedTask<BlockingSchedule>, |
| mandatory: Mandatory, |
| } |
| |
| <span class="attribute">#[derive(PartialEq, Eq)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>Mandatory { |
| <span class="attribute">#[cfg_attr(not(fs), allow(dead_code))] |
| </span>Mandatory, |
| NonMandatory, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>SpawnError { |
| <span class="doccomment">/// Pool is shutting down and the task was not scheduled |
| </span>ShuttingDown, |
| <span class="doccomment">/// There are no worker threads available to take the task |
| /// and the OS failed to spawn a new one |
| </span>NoThreads(io::Error), |
| } |
| |
| <span class="kw">impl </span>From<SpawnError> <span class="kw">for </span>io::Error { |
| <span class="kw">fn </span>from(e: SpawnError) -> <span class="self">Self </span>{ |
| <span class="kw">match </span>e { |
| SpawnError::ShuttingDown => { |
| io::Error::new(io::ErrorKind::Other, <span class="string">"blocking pool shutting down"</span>) |
| } |
| SpawnError::NoThreads(e) => e, |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Task { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(task: task::UnownedTask<BlockingSchedule>, mandatory: Mandatory) -> Task { |
| Task { task, mandatory } |
| } |
| |
| <span class="kw">fn </span>run(<span class="self">self</span>) { |
| <span class="self">self</span>.task.run(); |
| } |
| |
| <span class="kw">fn </span>shutdown_or_run_if_mandatory(<span class="self">self</span>) { |
| <span class="kw">match </span><span class="self">self</span>.mandatory { |
| Mandatory::NonMandatory => <span class="self">self</span>.task.shutdown(), |
| Mandatory::Mandatory => <span class="self">self</span>.task.run(), |
| } |
| } |
| } |
| |
| <span class="kw">const </span>KEEP_ALIVE: Duration = Duration::from_secs(<span class="number">10</span>); |
| |
| <span class="doccomment">/// Runs the provided function on an executor dedicated to blocking operations. |
| /// Tasks will be scheduled as non-mandatory, meaning they may not get executed |
| /// in case of runtime shutdown. |
| </span><span class="attribute">#[track_caller] |
| #[cfg_attr(tokio_wasi, allow(dead_code))] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_blocking<F, R>(func: F) -> JoinHandle<R> |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>rt = Handle::current(); |
| rt.spawn_blocking(func) |
| } |
| |
| <span class="macro">cfg_fs! </span>{ |
| <span class="attribute">#[cfg_attr(any( |
| all(loom, not(test)), <span class="comment">// the function is covered by loom tests |
| </span>test |
| ), allow(dead_code))] |
| </span><span class="doccomment">/// Runs the provided function on an executor dedicated to blocking |
| /// operations. Tasks will be scheduled as mandatory, meaning they are |
| /// guaranteed to run unless a shutdown is already taking place. In case a |
| /// shutdown is already taking place, `None` will be returned. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_mandatory_blocking<F, R>(func: F) -> <span class="prelude-ty">Option</span><JoinHandle<R>> |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>rt = Handle::current(); |
| rt.inner.blocking_spawner().spawn_mandatory_blocking(<span class="kw-2">&</span>rt, func) |
| } |
| } |
| |
| <span class="comment">// ===== impl BlockingPool ===== |
| |
| </span><span class="kw">impl </span>BlockingPool { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(builder: <span class="kw-2">&</span>Builder, thread_cap: usize) -> BlockingPool { |
| <span class="kw">let </span>(shutdown_tx, shutdown_rx) = shutdown::channel(); |
| <span class="kw">let </span>keep_alive = builder.keep_alive.unwrap_or(KEEP_ALIVE); |
| |
| BlockingPool { |
| spawner: Spawner { |
| inner: Arc::new(Inner { |
| shared: Mutex::new(Shared { |
| queue: VecDeque::new(), |
| num_notify: <span class="number">0</span>, |
| shutdown: <span class="bool-val">false</span>, |
| shutdown_tx: <span class="prelude-val">Some</span>(shutdown_tx), |
| last_exiting_thread: <span class="prelude-val">None</span>, |
| worker_threads: HashMap::new(), |
| worker_thread_index: <span class="number">0</span>, |
| }), |
| condvar: Condvar::new(), |
| thread_name: builder.thread_name.clone(), |
| stack_size: builder.thread_stack_size, |
| after_start: builder.after_start.clone(), |
| before_stop: builder.before_stop.clone(), |
| thread_cap, |
| keep_alive, |
| metrics: Default::default(), |
| }), |
| }, |
| shutdown_rx, |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawner(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>Spawner { |
| <span class="kw-2">&</span><span class="self">self</span>.spawner |
| } |
| |
| <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>, timeout: <span class="prelude-ty">Option</span><Duration>) { |
| <span class="kw">let </span><span class="kw-2">mut </span>shared = <span class="self">self</span>.spawner.inner.shared.lock(); |
| |
| <span class="comment">// The function can be called multiple times. First, by explicitly |
| // calling `shutdown` then by the drop handler calling `shutdown`. This |
| // prevents shutting down twice. |
| </span><span class="kw">if </span>shared.shutdown { |
| <span class="kw">return</span>; |
| } |
| |
| shared.shutdown = <span class="bool-val">true</span>; |
| shared.shutdown_tx = <span class="prelude-val">None</span>; |
| <span class="self">self</span>.spawner.inner.condvar.notify_all(); |
| |
| <span class="kw">let </span>last_exited_thread = std::mem::take(<span class="kw-2">&mut </span>shared.last_exiting_thread); |
| <span class="kw">let </span>workers = std::mem::take(<span class="kw-2">&mut </span>shared.worker_threads); |
| |
| drop(shared); |
| |
| <span class="kw">if </span><span class="self">self</span>.shutdown_rx.wait(timeout) { |
| <span class="kw">let _ </span>= last_exited_thread.map(|th| th.join()); |
| |
| <span class="comment">// Loom requires that execution be deterministic, so sort by thread ID before joining. |
| // (HashMaps use a randomly-seeded hash function, so the order is nondeterministic) |
| </span><span class="kw">let </span><span class="kw-2">mut </span>workers: Vec<(usize, thread::JoinHandle<()>)> = workers.into_iter().collect(); |
| workers.sort_by_key(|(id, <span class="kw">_</span>)| <span class="kw-2">*</span>id); |
| |
| <span class="kw">for </span>(_id, handle) <span class="kw">in </span>workers.into_iter() { |
| <span class="kw">let _ </span>= handle.join(); |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>BlockingPool { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.shutdown(<span class="prelude-val">None</span>); |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>BlockingPool { |
| <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 { |
| fmt.debug_struct(<span class="string">"BlockingPool"</span>).finish() |
| } |
| } |
| |
| <span class="comment">// ===== impl Spawner ===== |
| |
| </span><span class="kw">impl </span>Spawner { |
| <span class="attribute">#[track_caller] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_blocking<F, R>(<span class="kw-2">&</span><span class="self">self</span>, rt: <span class="kw-2">&</span>Handle, func: F) -> JoinHandle<R> |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>(join_handle, spawn_result) = |
| <span class="kw">if </span><span class="macro">cfg!</span>(debug_assertions) && std::mem::size_of::<F>() > <span class="number">2048 </span>{ |
| <span class="self">self</span>.spawn_blocking_inner(Box::new(func), Mandatory::NonMandatory, <span class="prelude-val">None</span>, rt) |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.spawn_blocking_inner(func, Mandatory::NonMandatory, <span class="prelude-val">None</span>, rt) |
| }; |
| |
| <span class="kw">match </span>spawn_result { |
| <span class="prelude-val">Ok</span>(()) => join_handle, |
| <span class="comment">// Compat: do not panic here, return the join_handle even though it will never resolve |
| </span><span class="prelude-val">Err</span>(SpawnError::ShuttingDown) => join_handle, |
| <span class="prelude-val">Err</span>(SpawnError::NoThreads(e)) => { |
| <span class="macro">panic!</span>(<span class="string">"OS can't spawn worker thread: {}"</span>, e) |
| } |
| } |
| } |
| |
| <span class="macro">cfg_fs! </span>{ |
| <span class="attribute">#[track_caller] |
| #[cfg_attr(any( |
| all(loom, not(test)), <span class="comment">// the function is covered by loom tests |
| </span>test |
| ), allow(dead_code))] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_mandatory_blocking<F, R>(<span class="kw-2">&</span><span class="self">self</span>, rt: <span class="kw-2">&</span>Handle, func: F) -> <span class="prelude-ty">Option</span><JoinHandle<R>> |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>(join_handle, spawn_result) = <span class="kw">if </span><span class="macro">cfg!</span>(debug_assertions) && std::mem::size_of::<F>() > <span class="number">2048 </span>{ |
| <span class="self">self</span>.spawn_blocking_inner( |
| Box::new(func), |
| Mandatory::Mandatory, |
| <span class="prelude-val">None</span>, |
| rt, |
| ) |
| } <span class="kw">else </span>{ |
| <span class="self">self</span>.spawn_blocking_inner( |
| func, |
| Mandatory::Mandatory, |
| <span class="prelude-val">None</span>, |
| rt, |
| ) |
| }; |
| |
| <span class="kw">if </span>spawn_result.is_ok() { |
| <span class="prelude-val">Some</span>(join_handle) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| } |
| |
| <span class="attribute">#[track_caller] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>spawn_blocking_inner<F, R>( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| func: F, |
| is_mandatory: Mandatory, |
| name: <span class="prelude-ty">Option</span><<span class="kw-2">&</span>str>, |
| rt: <span class="kw-2">&</span>Handle, |
| ) -> (JoinHandle<R>, <span class="prelude-ty">Result</span><(), SpawnError>) |
| <span class="kw">where |
| </span>F: FnOnce() -> R + Send + <span class="lifetime">'static</span>, |
| R: Send + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>fut = BlockingTask::new(func); |
| <span class="kw">let </span>id = task::Id::next(); |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">let </span>fut = { |
| <span class="kw">use </span>tracing::Instrument; |
| <span class="kw">let </span>location = std::panic::Location::caller(); |
| <span class="kw">let </span>span = <span class="macro">tracing::trace_span!</span>( |
| target: <span class="string">"tokio::task::blocking"</span>, |
| <span class="string">"runtime.spawn"</span>, |
| kind = %<span class="string">"blocking"</span>, |
| task.name = %name.unwrap_or_default(), |
| task.id = id.as_u64(), |
| <span class="string">"fn" </span>= %std::any::type_name::<F>(), |
| spawn.location = %<span class="macro">format_args!</span>(<span class="string">"{}:{}:{}"</span>, location.file(), location.line(), location.column()), |
| ); |
| fut.instrument(span) |
| }; |
| |
| <span class="attribute">#[cfg(not(all(tokio_unstable, feature = <span class="string">"tracing"</span>)))] |
| </span><span class="kw">let _ </span>= name; |
| |
| <span class="kw">let </span>(task, handle) = task::unowned(fut, BlockingSchedule::new(rt), id); |
| |
| <span class="kw">let </span>spawned = <span class="self">self</span>.spawn_task(Task::new(task, is_mandatory), rt); |
| (handle, spawned) |
| } |
| |
| <span class="kw">fn </span>spawn_task(<span class="kw-2">&</span><span class="self">self</span>, task: Task, rt: <span class="kw-2">&</span>Handle) -> <span class="prelude-ty">Result</span><(), SpawnError> { |
| <span class="kw">let </span><span class="kw-2">mut </span>shared = <span class="self">self</span>.inner.shared.lock(); |
| |
| <span class="kw">if </span>shared.shutdown { |
| <span class="comment">// Shutdown the task: it's fine to shutdown this task (even if |
| // mandatory) because it was scheduled after the shutdown of the |
| // runtime began. |
| </span>task.task.shutdown(); |
| |
| <span class="comment">// no need to even push this task; it would never get picked up |
| </span><span class="kw">return </span><span class="prelude-val">Err</span>(SpawnError::ShuttingDown); |
| } |
| |
| shared.queue.push_back(task); |
| <span class="self">self</span>.inner.metrics.inc_queue_depth(); |
| |
| <span class="kw">if </span><span class="self">self</span>.inner.metrics.num_idle_threads() == <span class="number">0 </span>{ |
| <span class="comment">// No threads are able to process the task. |
| |
| </span><span class="kw">if </span><span class="self">self</span>.inner.metrics.num_threads() == <span class="self">self</span>.inner.thread_cap { |
| <span class="comment">// At max number of threads |
| </span>} <span class="kw">else </span>{ |
| <span class="macro">assert!</span>(shared.shutdown_tx.is_some()); |
| <span class="kw">let </span>shutdown_tx = shared.shutdown_tx.clone(); |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(shutdown_tx) = shutdown_tx { |
| <span class="kw">let </span>id = shared.worker_thread_index; |
| |
| <span class="kw">match </span><span class="self">self</span>.spawn_thread(shutdown_tx, rt, id) { |
| <span class="prelude-val">Ok</span>(handle) => { |
| <span class="self">self</span>.inner.metrics.inc_num_threads(); |
| shared.worker_thread_index += <span class="number">1</span>; |
| shared.worker_threads.insert(id, handle); |
| } |
| <span class="prelude-val">Err</span>(<span class="kw-2">ref </span>e) |
| <span class="kw">if </span>is_temporary_os_thread_error(e) |
| && <span class="self">self</span>.inner.metrics.num_threads() > <span class="number">0 </span>=> |
| { |
| <span class="comment">// OS temporarily failed to spawn a new thread. |
| // The task will be picked up eventually by a currently |
| // busy thread. |
| </span>} |
| <span class="prelude-val">Err</span>(e) => { |
| <span class="comment">// The OS refused to spawn the thread and there is no thread |
| // to pick up the task that has just been pushed to the queue. |
| </span><span class="kw">return </span><span class="prelude-val">Err</span>(SpawnError::NoThreads(e)); |
| } |
| } |
| } |
| } |
| } <span class="kw">else </span>{ |
| <span class="comment">// Notify an idle worker thread. The notification counter |
| // is used to count the needed amount of notifications |
| // exactly. Thread libraries may generate spurious |
| // wakeups, this counter is used to keep us in a |
| // consistent state. |
| </span><span class="self">self</span>.inner.metrics.dec_num_idle_threads(); |
| shared.num_notify += <span class="number">1</span>; |
| <span class="self">self</span>.inner.condvar.notify_one(); |
| } |
| |
| <span class="prelude-val">Ok</span>(()) |
| } |
| |
| <span class="kw">fn </span>spawn_thread( |
| <span class="kw-2">&</span><span class="self">self</span>, |
| shutdown_tx: shutdown::Sender, |
| rt: <span class="kw-2">&</span>Handle, |
| id: usize, |
| ) -> std::io::Result<thread::JoinHandle<()>> { |
| <span class="kw">let </span><span class="kw-2">mut </span>builder = thread::Builder::new().name((<span class="self">self</span>.inner.thread_name)()); |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(stack_size) = <span class="self">self</span>.inner.stack_size { |
| builder = builder.stack_size(stack_size); |
| } |
| |
| <span class="kw">let </span>rt = rt.clone(); |
| |
| builder.spawn(<span class="kw">move </span>|| { |
| <span class="comment">// Only the reference should be moved into the closure |
| </span><span class="kw">let </span>_enter = rt.enter(); |
| rt.inner.blocking_spawner().inner.run(id); |
| drop(shutdown_tx); |
| }) |
| } |
| } |
| |
| <span class="macro">cfg_metrics! </span>{ |
| <span class="kw">impl </span>Spawner { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>num_threads(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.inner.metrics.num_threads() |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>num_idle_threads(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.inner.metrics.num_idle_threads() |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>queue_depth(<span class="kw-2">&</span><span class="self">self</span>) -> usize { |
| <span class="self">self</span>.inner.metrics.queue_depth() |
| } |
| } |
| } |
| |
| <span class="comment">// Tells whether the error when spawning a thread is temporary. |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">fn </span>is_temporary_os_thread_error(error: <span class="kw-2">&</span>std::io::Error) -> bool { |
| <span class="macro">matches!</span>(error.kind(), std::io::ErrorKind::WouldBlock) |
| } |
| |
| <span class="kw">impl </span>Inner { |
| <span class="kw">fn </span>run(<span class="kw-2">&</span><span class="self">self</span>, worker_thread_id: usize) { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(f) = <span class="kw-2">&</span><span class="self">self</span>.after_start { |
| f() |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>shared = <span class="self">self</span>.shared.lock(); |
| <span class="kw">let </span><span class="kw-2">mut </span>join_on_thread = <span class="prelude-val">None</span>; |
| |
| <span class="lifetime">'main</span>: <span class="kw">loop </span>{ |
| <span class="comment">// BUSY |
| </span><span class="kw">while let </span><span class="prelude-val">Some</span>(task) = shared.queue.pop_front() { |
| <span class="self">self</span>.metrics.dec_queue_depth(); |
| drop(shared); |
| task.run(); |
| |
| shared = <span class="self">self</span>.shared.lock(); |
| } |
| |
| <span class="comment">// IDLE |
| </span><span class="self">self</span>.metrics.inc_num_idle_threads(); |
| |
| <span class="kw">while </span>!shared.shutdown { |
| <span class="kw">let </span>lock_result = <span class="self">self</span>.condvar.wait_timeout(shared, <span class="self">self</span>.keep_alive).unwrap(); |
| |
| shared = lock_result.<span class="number">0</span>; |
| <span class="kw">let </span>timeout_result = lock_result.<span class="number">1</span>; |
| |
| <span class="kw">if </span>shared.num_notify != <span class="number">0 </span>{ |
| <span class="comment">// We have received a legitimate wakeup, |
| // acknowledge it by decrementing the counter |
| // and transition to the BUSY state. |
| </span>shared.num_notify -= <span class="number">1</span>; |
| <span class="kw">break</span>; |
| } |
| |
| <span class="comment">// Even if the condvar "timed out", if the pool is entering the |
| // shutdown phase, we want to perform the cleanup logic. |
| </span><span class="kw">if </span>!shared.shutdown && timeout_result.timed_out() { |
| <span class="comment">// We'll join the prior timed-out thread's JoinHandle after dropping the lock. |
| // This isn't done when shutting down, because the thread calling shutdown will |
| // handle joining everything. |
| </span><span class="kw">let </span>my_handle = shared.worker_threads.remove(<span class="kw-2">&</span>worker_thread_id); |
| join_on_thread = std::mem::replace(<span class="kw-2">&mut </span>shared.last_exiting_thread, my_handle); |
| |
| <span class="kw">break </span><span class="lifetime">'main</span>; |
| } |
| |
| <span class="comment">// Spurious wakeup detected, go back to sleep. |
| </span>} |
| |
| <span class="kw">if </span>shared.shutdown { |
| <span class="comment">// Drain the queue |
| </span><span class="kw">while let </span><span class="prelude-val">Some</span>(task) = shared.queue.pop_front() { |
| <span class="self">self</span>.metrics.dec_queue_depth(); |
| drop(shared); |
| |
| task.shutdown_or_run_if_mandatory(); |
| |
| shared = <span class="self">self</span>.shared.lock(); |
| } |
| |
| <span class="comment">// Work was produced, and we "took" it (by decrementing num_notify). |
| // This means that num_idle was decremented once for our wakeup. |
| // But, since we are exiting, we need to "undo" that, as we'll stay idle. |
| </span><span class="self">self</span>.metrics.inc_num_idle_threads(); |
| <span class="comment">// NOTE: Technically we should also do num_notify++ and notify again, |
| // but since we're shutting down anyway, that won't be necessary. |
| </span><span class="kw">break</span>; |
| } |
| } |
| |
| <span class="comment">// Thread exit |
| </span><span class="self">self</span>.metrics.dec_num_threads(); |
| |
| <span class="comment">// num_idle should now be tracked exactly, panic |
| // with a descriptive message if it is not the |
| // case. |
| </span><span class="kw">let </span>prev_idle = <span class="self">self</span>.metrics.dec_num_idle_threads(); |
| <span class="kw">if </span>prev_idle < <span class="self">self</span>.metrics.num_idle_threads() { |
| <span class="macro">panic!</span>(<span class="string">"num_idle_threads underflowed on thread exit"</span>) |
| } |
| |
| <span class="kw">if </span>shared.shutdown && <span class="self">self</span>.metrics.num_threads() == <span class="number">0 </span>{ |
| <span class="self">self</span>.condvar.notify_one(); |
| } |
| |
| drop(shared); |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(f) = <span class="kw-2">&</span><span class="self">self</span>.before_stop { |
| f() |
| } |
| |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(handle) = join_on_thread { |
| <span class="kw">let _ </span>= handle.join(); |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Spawner { |
| <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 { |
| fmt.debug_struct(<span class="string">"blocking::Spawner"</span>).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> |
