| <!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/context.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>context.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>::loom::thread::AccessError; |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::coop; |
| |
| <span class="kw">use </span>std::cell::Cell; |
| |
| <span class="attribute">#[cfg(any(feature = <span class="string">"rt"</span>, feature = <span class="string">"macros"</span>))] |
| </span><span class="kw">use </span><span class="kw">crate</span>::util::rand::{FastRand, RngSeed}; |
| |
| <span class="macro">cfg_rt! </span>{ |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::{scheduler, task::Id, Defer}; |
| |
| <span class="kw">use </span>std::cell::RefCell; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::time::Duration; |
| } |
| |
| <span class="kw">struct </span>Context { |
| <span class="doccomment">/// Uniquely identifies the current thread |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>thread_id: Cell<<span class="prelude-ty">Option</span><ThreadId>>, |
| |
| <span class="doccomment">/// Handle to the runtime scheduler running on the current thread. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>handle: RefCell<<span class="prelude-ty">Option</span><scheduler::Handle>>, |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>current_task_id: Cell<<span class="prelude-ty">Option</span><Id>>, |
| |
| <span class="doccomment">/// Tracks if the current thread is currently driving a runtime. |
| /// Note, that if this is set to "entered", the current scheduler |
| /// handle may not reference the runtime currently executing. This |
| /// is because other runtime handles may be set to current from |
| /// within a runtime. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>runtime: Cell<EnterRuntime>, |
| |
| <span class="doccomment">/// Yielded task wakers are stored here and notified after resource drivers |
| /// are polled. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>defer: RefCell<<span class="prelude-ty">Option</span><Defer>>, |
| |
| <span class="attribute">#[cfg(any(feature = <span class="string">"rt"</span>, feature = <span class="string">"macros"</span>))] |
| </span>rng: FastRand, |
| |
| <span class="doccomment">/// Tracks the amount of "work" a task may still do before yielding back to |
| /// the sheduler |
| </span>budget: Cell<coop::Budget>, |
| } |
| |
| <span class="macro">tokio_thread_local! </span>{ |
| <span class="kw">static </span>CONTEXT: Context = { |
| Context { |
| <span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>thread_id: Cell::new(<span class="prelude-val">None</span>), |
| |
| <span class="doccomment">/// Tracks the current runtime handle to use when spawning, |
| /// accessing drivers, etc... |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>handle: RefCell::new(<span class="prelude-val">None</span>), |
| <span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>current_task_id: Cell::new(<span class="prelude-val">None</span>), |
| |
| <span class="doccomment">/// Tracks if the current thread is currently driving a runtime. |
| /// Note, that if this is set to "entered", the current scheduler |
| /// handle may not reference the runtime currently executing. This |
| /// is because other runtime handles may be set to current from |
| /// within a runtime. |
| </span><span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>runtime: Cell::new(EnterRuntime::NotEntered), |
| |
| <span class="attribute">#[cfg(feature = <span class="string">"rt"</span>)] |
| </span>defer: RefCell::new(<span class="prelude-val">None</span>), |
| |
| <span class="attribute">#[cfg(any(feature = <span class="string">"rt"</span>, feature = <span class="string">"macros"</span>))] |
| </span>rng: FastRand::new(RngSeed::new()), |
| |
| budget: Cell::new(coop::Budget::unconstrained()), |
| } |
| } |
| } |
| |
| <span class="attribute">#[cfg(any(feature = <span class="string">"macros"</span>, all(feature = <span class="string">"sync"</span>, feature = <span class="string">"rt"</span>)))] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>thread_rng_n(n: u32) -> u32 { |
| CONTEXT.with(|ctx| ctx.rng.fastrand_n(n)) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>budget<R>(f: <span class="kw">impl </span>FnOnce(<span class="kw-2">&</span>Cell<coop::Budget>) -> R) -> <span class="prelude-ty">Result</span><R, AccessError> { |
| CONTEXT.try_with(|ctx| f(<span class="kw-2">&</span>ctx.budget)) |
| } |
| |
| <span class="macro">cfg_rt! </span>{ |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::{ThreadId, TryCurrentError}; |
| |
| <span class="kw">use </span>std::fmt; |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>thread_id() -> <span class="prelude-ty">Result</span><ThreadId, AccessError> { |
| CONTEXT.try_with(|ctx| { |
| <span class="kw">match </span>ctx.thread_id.get() { |
| <span class="prelude-val">Some</span>(id) => id, |
| <span class="prelude-val">None </span>=> { |
| <span class="kw">let </span>id = ThreadId::next(); |
| ctx.thread_id.set(<span class="prelude-val">Some</span>(id)); |
| id |
| } |
| } |
| }) |
| } |
| |
| <span class="attribute">#[derive(Debug, Clone, Copy)] |
| #[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">enum </span>EnterRuntime { |
| <span class="doccomment">/// Currently in a runtime context. |
| </span><span class="attribute">#[cfg_attr(not(feature = <span class="string">"rt"</span>), allow(dead_code))] |
| </span>Entered { allow_block_in_place: bool }, |
| |
| <span class="doccomment">/// Not in a runtime context **or** a blocking region. |
| </span>NotEntered, |
| } |
| |
| <span class="attribute">#[derive(Debug)] |
| #[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>SetCurrentGuard { |
| old_handle: <span class="prelude-ty">Option</span><scheduler::Handle>, |
| old_seed: RngSeed, |
| } |
| |
| <span class="doccomment">/// Guard tracking that a caller has entered a runtime context. |
| </span><span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>EnterRuntimeGuard { |
| <span class="doccomment">/// Tracks that the current thread has entered a blocking function call. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) blocking: BlockingRegionGuard, |
| |
| <span class="attribute">#[allow(dead_code)] </span><span class="comment">// Only tracking the guard. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) handle: SetCurrentGuard, |
| |
| <span class="doccomment">/// If true, then this is the root runtime guard. It is possible to nest |
| /// runtime guards by using `block_in_place` between the calls. We need |
| /// to track the root guard as this is the guard responsible for freeing |
| /// the deferred task queue. |
| </span>is_root: bool, |
| } |
| |
| <span class="doccomment">/// Guard tracking that a caller has entered a blocking region. |
| </span><span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>BlockingRegionGuard { |
| _p: PhantomData<RefCell<()>>, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>DisallowBlockInPlaceGuard(bool); |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>set_current_task_id(id: <span class="prelude-ty">Option</span><Id>) -> <span class="prelude-ty">Option</span><Id> { |
| CONTEXT.try_with(|ctx| ctx.current_task_id.replace(id)).unwrap_or(<span class="prelude-val">None</span>) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>current_task_id() -> <span class="prelude-ty">Option</span><Id> { |
| CONTEXT.try_with(|ctx| ctx.current_task_id.get()).unwrap_or(<span class="prelude-val">None</span>) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>try_current() -> <span class="prelude-ty">Result</span><scheduler::Handle, TryCurrentError> { |
| <span class="kw">match </span>CONTEXT.try_with(|ctx| ctx.handle.borrow().clone()) { |
| <span class="prelude-val">Ok</span>(<span class="prelude-val">Some</span>(handle)) => <span class="prelude-val">Ok</span>(handle), |
| <span class="prelude-val">Ok</span>(<span class="prelude-val">None</span>) => <span class="prelude-val">Err</span>(TryCurrentError::new_no_context()), |
| <span class="prelude-val">Err</span>(_access_error) => <span class="prelude-val">Err</span>(TryCurrentError::new_thread_local_destroyed()), |
| } |
| } |
| |
| <span class="doccomment">/// Sets this [`Handle`] as the current active [`Handle`]. |
| /// |
| /// [`Handle`]: crate::runtime::scheduler::Handle |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>try_set_current(handle: <span class="kw-2">&</span>scheduler::Handle) -> <span class="prelude-ty">Option</span><SetCurrentGuard> { |
| CONTEXT.try_with(|ctx| ctx.set_current(handle)).ok() |
| } |
| |
| |
| <span class="doccomment">/// Marks the current thread as being within the dynamic extent of an |
| /// executor. |
| </span><span class="attribute">#[track_caller] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>enter_runtime(handle: <span class="kw-2">&</span>scheduler::Handle, allow_block_in_place: bool) -> EnterRuntimeGuard { |
| <span class="kw">if let </span><span class="prelude-val">Some</span>(enter) = try_enter_runtime(handle, allow_block_in_place) { |
| <span class="kw">return </span>enter; |
| } |
| |
| <span class="macro">panic!</span>( |
| <span class="string">"Cannot start a runtime from within a runtime. This happens \ |
| because a function (like `block_on`) attempted to block the \ |
| current thread while the thread is being used to drive \ |
| asynchronous tasks." |
| </span>); |
| } |
| |
| <span class="doccomment">/// Tries to enter a runtime context, returns `None` if already in a runtime |
| /// context. |
| </span><span class="kw">fn </span>try_enter_runtime(handle: <span class="kw-2">&</span>scheduler::Handle, allow_block_in_place: bool) -> <span class="prelude-ty">Option</span><EnterRuntimeGuard> { |
| CONTEXT.with(|c| { |
| <span class="kw">if </span>c.runtime.get().is_entered() { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="comment">// Set the entered flag |
| </span>c.runtime.set(EnterRuntime::Entered { allow_block_in_place }); |
| |
| <span class="comment">// Initialize queue to track yielded tasks |
| </span><span class="kw">let </span><span class="kw-2">mut </span>defer = c.defer.borrow_mut(); |
| |
| <span class="kw">let </span>is_root = <span class="kw">if </span>defer.is_none() { |
| <span class="kw-2">*</span>defer = <span class="prelude-val">Some</span>(Defer::new()); |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>}; |
| |
| <span class="prelude-val">Some</span>(EnterRuntimeGuard { |
| blocking: BlockingRegionGuard::new(), |
| handle: c.set_current(handle), |
| is_root, |
| }) |
| } |
| }) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>try_enter_blocking_region() -> <span class="prelude-ty">Option</span><BlockingRegionGuard> { |
| CONTEXT.try_with(|c| { |
| <span class="kw">if </span>c.runtime.get().is_entered() { |
| <span class="prelude-val">None |
| </span>} <span class="kw">else </span>{ |
| <span class="prelude-val">Some</span>(BlockingRegionGuard::new()) |
| } |
| <span class="comment">// If accessing the thread-local fails, the thread is terminating |
| // and thread-locals are being destroyed. Because we don't know if |
| // we are currently in a runtime or not, we default to being |
| // permissive. |
| </span>}).unwrap_or_else(|<span class="kw">_</span>| <span class="prelude-val">Some</span>(BlockingRegionGuard::new())) |
| } |
| |
| <span class="doccomment">/// Disallows blocking in the current runtime context until the guard is dropped. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>disallow_block_in_place() -> DisallowBlockInPlaceGuard { |
| <span class="kw">let </span>reset = CONTEXT.with(|c| { |
| <span class="kw">if let </span>EnterRuntime::Entered { |
| allow_block_in_place: <span class="bool-val">true</span>, |
| } = c.runtime.get() |
| { |
| c.runtime.set(EnterRuntime::Entered { |
| allow_block_in_place: <span class="bool-val">false</span>, |
| }); |
| <span class="bool-val">true |
| </span>} <span class="kw">else </span>{ |
| <span class="bool-val">false |
| </span>} |
| }); |
| |
| DisallowBlockInPlaceGuard(reset) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>with_defer<R>(f: <span class="kw">impl </span>FnOnce(<span class="kw-2">&mut </span>Defer) -> R) -> <span class="prelude-ty">Option</span><R> { |
| CONTEXT.with(|c| { |
| <span class="kw">let </span><span class="kw-2">mut </span>defer = c.defer.borrow_mut(); |
| defer.as_mut().map(f) |
| }) |
| } |
| |
| <span class="kw">impl </span>Context { |
| <span class="kw">fn </span>set_current(<span class="kw-2">&</span><span class="self">self</span>, handle: <span class="kw-2">&</span>scheduler::Handle) -> SetCurrentGuard { |
| <span class="kw">let </span>rng_seed = handle.seed_generator().next_seed(); |
| |
| <span class="kw">let </span>old_handle = <span class="self">self</span>.handle.borrow_mut().replace(handle.clone()); |
| <span class="kw">let </span>old_seed = <span class="self">self</span>.rng.replace_seed(rng_seed); |
| |
| SetCurrentGuard { |
| old_handle, |
| old_seed, |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>SetCurrentGuard { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| CONTEXT.with(|ctx| { |
| <span class="kw-2">*</span>ctx.handle.borrow_mut() = <span class="self">self</span>.old_handle.take(); |
| ctx.rng.replace_seed(<span class="self">self</span>.old_seed.clone()); |
| }); |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>EnterRuntimeGuard { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"Enter"</span>).finish() |
| } |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>EnterRuntimeGuard { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| CONTEXT.with(|c| { |
| <span class="macro">assert!</span>(c.runtime.get().is_entered()); |
| c.runtime.set(EnterRuntime::NotEntered); |
| |
| <span class="kw">if </span><span class="self">self</span>.is_root { |
| <span class="kw-2">*</span>c.defer.borrow_mut() = <span class="prelude-val">None</span>; |
| } |
| }); |
| } |
| } |
| |
| <span class="kw">impl </span>BlockingRegionGuard { |
| <span class="kw">fn </span>new() -> BlockingRegionGuard { |
| BlockingRegionGuard { _p: PhantomData } |
| } |
| <span class="doccomment">/// Blocks the thread on the specified future, returning the value with |
| /// which that future completes. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>block_on<F>(<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">where |
| </span>F: std::future::Future, |
| { |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::park::CachedParkThread; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>park = CachedParkThread::new(); |
| park.block_on(f) |
| } |
| |
| <span class="doccomment">/// Blocks the thread on the specified future for **at most** `timeout` |
| /// |
| /// If the future completes before `timeout`, the result is returned. If |
| /// `timeout` elapses, then `Err` is returned. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>block_on_timeout<F>(<span class="kw-2">&mut </span><span class="self">self</span>, f: F, timeout: Duration) -> <span class="prelude-ty">Result</span><F::Output, ()> |
| <span class="kw">where |
| </span>F: std::future::Future, |
| { |
| <span class="kw">use </span><span class="kw">crate</span>::runtime::park::CachedParkThread; |
| <span class="kw">use </span>std::task::Context; |
| <span class="kw">use </span>std::task::Poll::Ready; |
| <span class="kw">use </span>std::time::Instant; |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>park = CachedParkThread::new(); |
| <span class="kw">let </span>waker = park.waker().map_err(|<span class="kw">_</span>| ())<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">let </span>when = Instant::now() + timeout; |
| |
| <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="kw">let </span>now = Instant::now(); |
| |
| <span class="kw">if </span>now >= when { |
| <span class="kw">return </span><span class="prelude-val">Err</span>(()); |
| } |
| |
| <span class="comment">// Wake any yielded tasks before parking in order to avoid |
| // blocking. |
| </span>with_defer(|defer| defer.wake()); |
| |
| park.park_timeout(when - now); |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>DisallowBlockInPlaceGuard { |
| <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>.<span class="number">0 </span>{ |
| <span class="comment">// XXX: Do we want some kind of assertion here, or is "best effort" okay? |
| </span>CONTEXT.with(|c| { |
| <span class="kw">if let </span>EnterRuntime::Entered { |
| allow_block_in_place: <span class="bool-val">false</span>, |
| } = c.runtime.get() |
| { |
| c.runtime.set(EnterRuntime::Entered { |
| allow_block_in_place: <span class="bool-val">true</span>, |
| }); |
| } |
| }) |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>EnterRuntime { |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>is_entered(<span class="self">self</span>) -> bool { |
| <span class="macro">matches!</span>(<span class="self">self</span>, EnterRuntime::Entered { .. }) |
| } |
| } |
| } |
| |
| <span class="comment">// Forces the current "entered" state to be cleared while the closure |
| // is executed. |
| // |
| // # Warning |
| // |
| // This is hidden for a reason. Do not use without fully understanding |
| // executors. Misusing can easily cause your program to deadlock. |
| </span><span class="macro">cfg_rt_multi_thread! </span>{ |
| <span class="doccomment">/// Returns true if in a runtime context. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>current_enter_context() -> EnterRuntime { |
| CONTEXT.with(|c| c.runtime.get()) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>exit_runtime<F: FnOnce() -> R, R>(f: F) -> R { |
| <span class="comment">// Reset in case the closure panics |
| </span><span class="kw">struct </span>Reset(EnterRuntime); |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>Reset { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| CONTEXT.with(|c| { |
| <span class="macro">assert!</span>(!c.runtime.get().is_entered(), <span class="string">"closure claimed permanent executor"</span>); |
| c.runtime.set(<span class="self">self</span>.<span class="number">0</span>); |
| }); |
| } |
| } |
| |
| <span class="kw">let </span>was = CONTEXT.with(|c| { |
| <span class="kw">let </span>e = c.runtime.get(); |
| <span class="macro">assert!</span>(e.is_entered(), <span class="string">"asked to exit when not entered"</span>); |
| c.runtime.set(EnterRuntime::NotEntered); |
| e |
| }); |
| |
| <span class="kw">let </span>_reset = Reset(was); |
| <span class="comment">// dropping _reset after f() will reset ENTERED |
| </span>f() |
| } |
| } |
| </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> |