| <!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/task/state.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>state.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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| <span id="523">523</span> |
| <span id="524">524</span> |
| <span id="525">525</span> |
| <span id="526">526</span> |
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| <span id="529">529</span> |
| <span id="530">530</span> |
| <span id="531">531</span> |
| <span id="532">532</span> |
| <span id="533">533</span> |
| <span id="534">534</span> |
| <span id="535">535</span> |
| <span id="536">536</span> |
| <span id="537">537</span> |
| <span id="538">538</span> |
| <span id="539">539</span> |
| <span id="540">540</span> |
| <span id="541">541</span> |
| <span id="542">542</span> |
| <span id="543">543</span> |
| <span id="544">544</span> |
| <span id="545">545</span> |
| <span id="546">546</span> |
| <span id="547">547</span> |
| <span id="548">548</span> |
| <span id="549">549</span> |
| <span id="550">550</span> |
| <span id="551">551</span> |
| <span id="552">552</span> |
| <span id="553">553</span> |
| <span id="554">554</span> |
| <span id="555">555</span> |
| <span id="556">556</span> |
| <span id="557">557</span> |
| <span id="558">558</span> |
| <span id="559">559</span> |
| <span id="560">560</span> |
| <span id="561">561</span> |
| <span id="562">562</span> |
| <span id="563">563</span> |
| <span id="564">564</span> |
| <span id="565">565</span> |
| <span id="566">566</span> |
| <span id="567">567</span> |
| <span id="568">568</span> |
| <span id="569">569</span> |
| <span id="570">570</span> |
| <span id="571">571</span> |
| <span id="572">572</span> |
| <span id="573">573</span> |
| <span id="574">574</span> |
| <span id="575">575</span> |
| <span id="576">576</span> |
| <span id="577">577</span> |
| <span id="578">578</span> |
| <span id="579">579</span> |
| <span id="580">580</span> |
| <span id="581">581</span> |
| <span id="582">582</span> |
| <span id="583">583</span> |
| <span id="584">584</span> |
| <span id="585">585</span> |
| <span id="586">586</span> |
| <span id="587">587</span> |
| <span id="588">588</span> |
| <span id="589">589</span> |
| <span id="590">590</span> |
| <span id="591">591</span> |
| <span id="592">592</span> |
| <span id="593">593</span> |
| <span id="594">594</span> |
| <span id="595">595</span> |
| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">crate</span>::loom::sync::atomic::AtomicUsize; |
| |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::sync::atomic::Ordering::{AcqRel, Acquire, Release}; |
| <span class="kw">use </span>std::usize; |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>State { |
| val: AtomicUsize, |
| } |
| |
| <span class="doccomment">/// Current state value. |
| </span><span class="attribute">#[derive(Copy, Clone)] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>Snapshot(usize); |
| |
| <span class="kw">type </span>UpdateResult = <span class="prelude-ty">Result</span><Snapshot, Snapshot>; |
| |
| <span class="doccomment">/// The task is currently being run. |
| </span><span class="kw">const </span>RUNNING: usize = <span class="number">0b0001</span>; |
| |
| <span class="doccomment">/// The task is complete. |
| /// |
| /// Once this bit is set, it is never unset. |
| </span><span class="kw">const </span>COMPLETE: usize = <span class="number">0b0010</span>; |
| |
| <span class="doccomment">/// Extracts the task's lifecycle value from the state. |
| </span><span class="kw">const </span>LIFECYCLE_MASK: usize = <span class="number">0b11</span>; |
| |
| <span class="doccomment">/// Flag tracking if the task has been pushed into a run queue. |
| </span><span class="kw">const </span>NOTIFIED: usize = <span class="number">0b100</span>; |
| |
| <span class="doccomment">/// The join handle is still around. |
| </span><span class="attribute">#[allow(clippy::unusual_byte_groupings)] </span><span class="comment">// https://github.com/rust-lang/rust-clippy/issues/6556 |
| </span><span class="kw">const </span>JOIN_INTEREST: usize = <span class="number">0b1_000</span>; |
| |
| <span class="doccomment">/// A join handle waker has been set. |
| </span><span class="attribute">#[allow(clippy::unusual_byte_groupings)] </span><span class="comment">// https://github.com/rust-lang/rust-clippy/issues/6556 |
| </span><span class="kw">const </span>JOIN_WAKER: usize = <span class="number">0b10_000</span>; |
| |
| <span class="doccomment">/// The task has been forcibly cancelled. |
| </span><span class="attribute">#[allow(clippy::unusual_byte_groupings)] </span><span class="comment">// https://github.com/rust-lang/rust-clippy/issues/6556 |
| </span><span class="kw">const </span>CANCELLED: usize = <span class="number">0b100_000</span>; |
| |
| <span class="doccomment">/// All bits. |
| </span><span class="kw">const </span>STATE_MASK: usize = LIFECYCLE_MASK | NOTIFIED | JOIN_INTEREST | JOIN_WAKER | CANCELLED; |
| |
| <span class="doccomment">/// Bits used by the ref count portion of the state. |
| </span><span class="kw">const </span>REF_COUNT_MASK: usize = !STATE_MASK; |
| |
| <span class="doccomment">/// Number of positions to shift the ref count. |
| </span><span class="kw">const </span>REF_COUNT_SHIFT: usize = REF_COUNT_MASK.count_zeros() <span class="kw">as </span>usize; |
| |
| <span class="doccomment">/// One ref count. |
| </span><span class="kw">const </span>REF_ONE: usize = <span class="number">1 </span><< REF_COUNT_SHIFT; |
| |
| <span class="doccomment">/// State a task is initialized with. |
| /// |
| /// A task is initialized with three references: |
| /// |
| /// * A reference that will be stored in an OwnedTasks or LocalOwnedTasks. |
| /// * A reference that will be sent to the scheduler as an ordinary notification. |
| /// * A reference for the JoinHandle. |
| /// |
| /// As the task starts with a `JoinHandle`, `JOIN_INTEREST` is set. |
| /// As the task starts with a `Notified`, `NOTIFIED` is set. |
| </span><span class="kw">const </span>INITIAL_STATE: usize = (REF_ONE * <span class="number">3</span>) | JOIN_INTEREST | NOTIFIED; |
| |
| <span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>TransitionToRunning { |
| Success, |
| Cancelled, |
| Failed, |
| Dealloc, |
| } |
| |
| <span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>TransitionToIdle { |
| <span class="prelude-val">Ok</span>, |
| OkNotified, |
| OkDealloc, |
| Cancelled, |
| } |
| |
| <span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>TransitionToNotifiedByVal { |
| DoNothing, |
| Submit, |
| Dealloc, |
| } |
| |
| <span class="attribute">#[must_use] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>TransitionToNotifiedByRef { |
| DoNothing, |
| Submit, |
| } |
| |
| <span class="doccomment">/// All transitions are performed via RMW operations. This establishes an |
| /// unambiguous modification order. |
| </span><span class="kw">impl </span>State { |
| <span class="doccomment">/// Returns a task's initial state. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>new() -> State { |
| <span class="comment">// The raw task returned by this method has a ref-count of three. See |
| // the comment on INITIAL_STATE for more. |
| </span>State { |
| val: AtomicUsize::new(INITIAL_STATE), |
| } |
| } |
| |
| <span class="doccomment">/// Loads the current state, establishes `Acquire` ordering. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>load(<span class="kw-2">&</span><span class="self">self</span>) -> Snapshot { |
| Snapshot(<span class="self">self</span>.val.load(Acquire)) |
| } |
| |
| <span class="doccomment">/// Attempts to transition the lifecycle to `Running`. This sets the |
| /// notified bit to false so notifications during the poll can be detected. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_running(<span class="kw-2">&</span><span class="self">self</span>) -> TransitionToRunning { |
| <span class="self">self</span>.fetch_update_action(|<span class="kw-2">mut </span>next| { |
| <span class="kw">let </span>action; |
| <span class="macro">assert!</span>(next.is_notified()); |
| |
| <span class="kw">if </span>!next.is_idle() { |
| <span class="comment">// This happens if the task is either currently running or if it |
| // has already completed, e.g. if it was cancelled during |
| // shutdown. Consume the ref-count and return. |
| </span>next.ref_dec(); |
| <span class="kw">if </span>next.ref_count() == <span class="number">0 </span>{ |
| action = TransitionToRunning::Dealloc; |
| } <span class="kw">else </span>{ |
| action = TransitionToRunning::Failed; |
| } |
| } <span class="kw">else </span>{ |
| <span class="comment">// We are able to lock the RUNNING bit. |
| </span>next.set_running(); |
| next.unset_notified(); |
| |
| <span class="kw">if </span>next.is_cancelled() { |
| action = TransitionToRunning::Cancelled; |
| } <span class="kw">else </span>{ |
| action = TransitionToRunning::Success; |
| } |
| } |
| (action, <span class="prelude-val">Some</span>(next)) |
| }) |
| } |
| |
| <span class="doccomment">/// Transitions the task from `Running` -> `Idle`. |
| /// |
| /// Returns `true` if the transition to `Idle` is successful, `false` otherwise. |
| /// The transition to `Idle` fails if the task has been flagged to be |
| /// cancelled. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_idle(<span class="kw-2">&</span><span class="self">self</span>) -> TransitionToIdle { |
| <span class="self">self</span>.fetch_update_action(|curr| { |
| <span class="macro">assert!</span>(curr.is_running()); |
| |
| <span class="kw">if </span>curr.is_cancelled() { |
| <span class="kw">return </span>(TransitionToIdle::Cancelled, <span class="prelude-val">None</span>); |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>next = curr; |
| <span class="kw">let </span>action; |
| next.unset_running(); |
| |
| <span class="kw">if </span>!next.is_notified() { |
| <span class="comment">// Polling the future consumes the ref-count of the Notified. |
| </span>next.ref_dec(); |
| <span class="kw">if </span>next.ref_count() == <span class="number">0 </span>{ |
| action = TransitionToIdle::OkDealloc; |
| } <span class="kw">else </span>{ |
| action = TransitionToIdle::Ok; |
| } |
| } <span class="kw">else </span>{ |
| <span class="comment">// The caller will schedule a new notification, so we create a |
| // new ref-count for the notification. Our own ref-count is kept |
| // for now, and the caller will drop it shortly. |
| </span>next.ref_inc(); |
| action = TransitionToIdle::OkNotified; |
| } |
| |
| (action, <span class="prelude-val">Some</span>(next)) |
| }) |
| } |
| |
| <span class="doccomment">/// Transitions the task from `Running` -> `Complete`. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_complete(<span class="kw-2">&</span><span class="self">self</span>) -> Snapshot { |
| <span class="kw">const </span>DELTA: usize = RUNNING | COMPLETE; |
| |
| <span class="kw">let </span>prev = Snapshot(<span class="self">self</span>.val.fetch_xor(DELTA, AcqRel)); |
| <span class="macro">assert!</span>(prev.is_running()); |
| <span class="macro">assert!</span>(!prev.is_complete()); |
| |
| Snapshot(prev.<span class="number">0 </span>^ DELTA) |
| } |
| |
| <span class="doccomment">/// Transitions from `Complete` -> `Terminal`, decrementing the reference |
| /// count the specified number of times. |
| /// |
| /// Returns true if the task should be deallocated. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_terminal(<span class="kw-2">&</span><span class="self">self</span>, count: usize) -> bool { |
| <span class="kw">let </span>prev = Snapshot(<span class="self">self</span>.val.fetch_sub(count * REF_ONE, AcqRel)); |
| <span class="macro">assert!</span>( |
| prev.ref_count() >= count, |
| <span class="string">"current: {}, sub: {}"</span>, |
| prev.ref_count(), |
| count |
| ); |
| prev.ref_count() == count |
| } |
| |
| <span class="doccomment">/// Transitions the state to `NOTIFIED`. |
| /// |
| /// If no task needs to be submitted, a ref-count is consumed. |
| /// |
| /// If a task needs to be submitted, the ref-count is incremented for the |
| /// new Notified. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_notified_by_val(<span class="kw-2">&</span><span class="self">self</span>) -> TransitionToNotifiedByVal { |
| <span class="self">self</span>.fetch_update_action(|<span class="kw-2">mut </span>snapshot| { |
| <span class="kw">let </span>action; |
| |
| <span class="kw">if </span>snapshot.is_running() { |
| <span class="comment">// If the task is running, we mark it as notified, but we should |
| // not submit anything as the thread currently running the |
| // future is responsible for that. |
| </span>snapshot.set_notified(); |
| snapshot.ref_dec(); |
| |
| <span class="comment">// The thread that set the running bit also holds a ref-count. |
| </span><span class="macro">assert!</span>(snapshot.ref_count() > <span class="number">0</span>); |
| |
| action = TransitionToNotifiedByVal::DoNothing; |
| } <span class="kw">else if </span>snapshot.is_complete() || snapshot.is_notified() { |
| <span class="comment">// We do not need to submit any notifications, but we have to |
| // decrement the ref-count. |
| </span>snapshot.ref_dec(); |
| |
| <span class="kw">if </span>snapshot.ref_count() == <span class="number">0 </span>{ |
| action = TransitionToNotifiedByVal::Dealloc; |
| } <span class="kw">else </span>{ |
| action = TransitionToNotifiedByVal::DoNothing; |
| } |
| } <span class="kw">else </span>{ |
| <span class="comment">// We create a new notified that we can submit. The caller |
| // retains ownership of the ref-count they passed in. |
| </span>snapshot.set_notified(); |
| snapshot.ref_inc(); |
| action = TransitionToNotifiedByVal::Submit; |
| } |
| |
| (action, <span class="prelude-val">Some</span>(snapshot)) |
| }) |
| } |
| |
| <span class="doccomment">/// Transitions the state to `NOTIFIED`. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_notified_by_ref(<span class="kw-2">&</span><span class="self">self</span>) -> TransitionToNotifiedByRef { |
| <span class="self">self</span>.fetch_update_action(|<span class="kw-2">mut </span>snapshot| { |
| <span class="kw">if </span>snapshot.is_complete() || snapshot.is_notified() { |
| <span class="comment">// There is nothing to do in this case. |
| </span>(TransitionToNotifiedByRef::DoNothing, <span class="prelude-val">None</span>) |
| } <span class="kw">else if </span>snapshot.is_running() { |
| <span class="comment">// If the task is running, we mark it as notified, but we should |
| // not submit as the thread currently running the future is |
| // responsible for that. |
| </span>snapshot.set_notified(); |
| (TransitionToNotifiedByRef::DoNothing, <span class="prelude-val">Some</span>(snapshot)) |
| } <span class="kw">else </span>{ |
| <span class="comment">// The task is idle and not notified. We should submit a |
| // notification. |
| </span>snapshot.set_notified(); |
| snapshot.ref_inc(); |
| (TransitionToNotifiedByRef::Submit, <span class="prelude-val">Some</span>(snapshot)) |
| } |
| }) |
| } |
| |
| <span class="doccomment">/// Sets the cancelled bit and transitions the state to `NOTIFIED` if idle. |
| /// |
| /// Returns `true` if the task needs to be submitted to the pool for |
| /// execution. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_notified_and_cancel(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="self">self</span>.fetch_update_action(|<span class="kw-2">mut </span>snapshot| { |
| <span class="kw">if </span>snapshot.is_cancelled() || snapshot.is_complete() { |
| <span class="comment">// Aborts to completed or cancelled tasks are no-ops. |
| </span>(<span class="bool-val">false</span>, <span class="prelude-val">None</span>) |
| } <span class="kw">else if </span>snapshot.is_running() { |
| <span class="comment">// If the task is running, we mark it as cancelled. The thread |
| // running the task will notice the cancelled bit when it |
| // stops polling and it will kill the task. |
| // |
| // The set_notified() call is not strictly necessary but it will |
| // in some cases let a wake_by_ref call return without having |
| // to perform a compare_exchange. |
| </span>snapshot.set_notified(); |
| snapshot.set_cancelled(); |
| (<span class="bool-val">false</span>, <span class="prelude-val">Some</span>(snapshot)) |
| } <span class="kw">else </span>{ |
| <span class="comment">// The task is idle. We set the cancelled and notified bits and |
| // submit a notification if the notified bit was not already |
| // set. |
| </span>snapshot.set_cancelled(); |
| <span class="kw">if </span>!snapshot.is_notified() { |
| snapshot.set_notified(); |
| snapshot.ref_inc(); |
| (<span class="bool-val">true</span>, <span class="prelude-val">Some</span>(snapshot)) |
| } <span class="kw">else </span>{ |
| (<span class="bool-val">false</span>, <span class="prelude-val">Some</span>(snapshot)) |
| } |
| } |
| }) |
| } |
| |
| <span class="doccomment">/// Sets the `CANCELLED` bit and attempts to transition to `Running`. |
| /// |
| /// Returns `true` if the transition to `Running` succeeded. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>transition_to_shutdown(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span><span class="kw-2">mut </span>prev = Snapshot(<span class="number">0</span>); |
| |
| <span class="kw">let _ </span>= <span class="self">self</span>.fetch_update(|<span class="kw-2">mut </span>snapshot| { |
| prev = snapshot; |
| |
| <span class="kw">if </span>snapshot.is_idle() { |
| snapshot.set_running(); |
| } |
| |
| <span class="comment">// If the task was not idle, the thread currently running the task |
| // will notice the cancelled bit and cancel it once the poll |
| // completes. |
| </span>snapshot.set_cancelled(); |
| <span class="prelude-val">Some</span>(snapshot) |
| }); |
| |
| prev.is_idle() |
| } |
| |
| <span class="doccomment">/// Optimistically tries to swap the state assuming the join handle is |
| /// __immediately__ dropped on spawn. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>drop_join_handle_fast(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><(), ()> { |
| <span class="kw">use </span>std::sync::atomic::Ordering::Relaxed; |
| |
| <span class="comment">// Relaxed is acceptable as if this function is called and succeeds, |
| // then nothing has been done w/ the join handle. |
| // |
| // The moment the join handle is used (polled), the `JOIN_WAKER` flag is |
| // set, at which point the CAS will fail. |
| // |
| // Given this, there is no risk if this operation is reordered. |
| </span><span class="self">self</span>.val |
| .compare_exchange_weak( |
| INITIAL_STATE, |
| (INITIAL_STATE - REF_ONE) & !JOIN_INTEREST, |
| Release, |
| Relaxed, |
| ) |
| .map(|<span class="kw">_</span>| ()) |
| .map_err(|<span class="kw">_</span>| ()) |
| } |
| |
| <span class="doccomment">/// Tries to unset the JOIN_INTEREST flag. |
| /// |
| /// Returns `Ok` if the operation happens before the task transitions to a |
| /// completed state, `Err` otherwise. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>unset_join_interested(<span class="kw-2">&</span><span class="self">self</span>) -> UpdateResult { |
| <span class="self">self</span>.fetch_update(|curr| { |
| <span class="macro">assert!</span>(curr.is_join_interested()); |
| |
| <span class="kw">if </span>curr.is_complete() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>next = curr; |
| next.unset_join_interested(); |
| |
| <span class="prelude-val">Some</span>(next) |
| }) |
| } |
| |
| <span class="doccomment">/// Sets the `JOIN_WAKER` bit. |
| /// |
| /// Returns `Ok` if the bit is set, `Err` otherwise. This operation fails if |
| /// the task has completed. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>set_join_waker(<span class="kw-2">&</span><span class="self">self</span>) -> UpdateResult { |
| <span class="self">self</span>.fetch_update(|curr| { |
| <span class="macro">assert!</span>(curr.is_join_interested()); |
| <span class="macro">assert!</span>(!curr.is_join_waker_set()); |
| |
| <span class="kw">if </span>curr.is_complete() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>next = curr; |
| next.set_join_waker(); |
| |
| <span class="prelude-val">Some</span>(next) |
| }) |
| } |
| |
| <span class="doccomment">/// Unsets the `JOIN_WAKER` bit. |
| /// |
| /// Returns `Ok` has been unset, `Err` otherwise. This operation fails if |
| /// the task has completed. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>unset_waker(<span class="kw-2">&</span><span class="self">self</span>) -> UpdateResult { |
| <span class="self">self</span>.fetch_update(|curr| { |
| <span class="macro">assert!</span>(curr.is_join_interested()); |
| <span class="macro">assert!</span>(curr.is_join_waker_set()); |
| |
| <span class="kw">if </span>curr.is_complete() { |
| <span class="kw">return </span><span class="prelude-val">None</span>; |
| } |
| |
| <span class="kw">let </span><span class="kw-2">mut </span>next = curr; |
| next.unset_join_waker(); |
| |
| <span class="prelude-val">Some</span>(next) |
| }) |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ref_inc(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">use </span>std::process; |
| <span class="kw">use </span>std::sync::atomic::Ordering::Relaxed; |
| |
| <span class="comment">// Using a relaxed ordering is alright here, as knowledge of the |
| // original reference prevents other threads from erroneously deleting |
| // the object. |
| // |
| // As explained in the [Boost documentation][1], Increasing the |
| // reference counter can always be done with memory_order_relaxed: New |
| // references to an object can only be formed from an existing |
| // reference, and passing an existing reference from one thread to |
| // another must already provide any required synchronization. |
| // |
| // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html) |
| </span><span class="kw">let </span>prev = <span class="self">self</span>.val.fetch_add(REF_ONE, Relaxed); |
| |
| <span class="comment">// If the reference count overflowed, abort. |
| </span><span class="kw">if </span>prev > isize::MAX <span class="kw">as </span>usize { |
| process::abort(); |
| } |
| } |
| |
| <span class="doccomment">/// Returns `true` if the task should be released. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ref_dec(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span>prev = Snapshot(<span class="self">self</span>.val.fetch_sub(REF_ONE, AcqRel)); |
| <span class="macro">assert!</span>(prev.ref_count() >= <span class="number">1</span>); |
| prev.ref_count() == <span class="number">1 |
| </span>} |
| |
| <span class="doccomment">/// Returns `true` if the task should be released. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ref_dec_twice(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| <span class="kw">let </span>prev = Snapshot(<span class="self">self</span>.val.fetch_sub(<span class="number">2 </span>* REF_ONE, AcqRel)); |
| <span class="macro">assert!</span>(prev.ref_count() >= <span class="number">2</span>); |
| prev.ref_count() == <span class="number">2 |
| </span>} |
| |
| <span class="kw">fn </span>fetch_update_action<F, T>(<span class="kw-2">&</span><span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> T |
| <span class="kw">where |
| </span>F: FnMut(Snapshot) -> (T, <span class="prelude-ty">Option</span><Snapshot>), |
| { |
| <span class="kw">let </span><span class="kw-2">mut </span>curr = <span class="self">self</span>.load(); |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">let </span>(output, next) = f(curr); |
| <span class="kw">let </span>next = <span class="kw">match </span>next { |
| <span class="prelude-val">Some</span>(next) => next, |
| <span class="prelude-val">None </span>=> <span class="kw">return </span>output, |
| }; |
| |
| <span class="kw">let </span>res = <span class="self">self</span>.val.compare_exchange(curr.<span class="number">0</span>, next.<span class="number">0</span>, AcqRel, Acquire); |
| |
| <span class="kw">match </span>res { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => <span class="kw">return </span>output, |
| <span class="prelude-val">Err</span>(actual) => curr = Snapshot(actual), |
| } |
| } |
| } |
| |
| <span class="kw">fn </span>fetch_update<F>(<span class="kw-2">&</span><span class="self">self</span>, <span class="kw-2">mut </span>f: F) -> <span class="prelude-ty">Result</span><Snapshot, Snapshot> |
| <span class="kw">where |
| </span>F: FnMut(Snapshot) -> <span class="prelude-ty">Option</span><Snapshot>, |
| { |
| <span class="kw">let </span><span class="kw-2">mut </span>curr = <span class="self">self</span>.load(); |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">let </span>next = <span class="kw">match </span>f(curr) { |
| <span class="prelude-val">Some</span>(next) => next, |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">Err</span>(curr), |
| }; |
| |
| <span class="kw">let </span>res = <span class="self">self</span>.val.compare_exchange(curr.<span class="number">0</span>, next.<span class="number">0</span>, AcqRel, Acquire); |
| |
| <span class="kw">match </span>res { |
| <span class="prelude-val">Ok</span>(<span class="kw">_</span>) => <span class="kw">return </span><span class="prelude-val">Ok</span>(next), |
| <span class="prelude-val">Err</span>(actual) => curr = Snapshot(actual), |
| } |
| } |
| } |
| } |
| |
| <span class="comment">// ===== impl Snapshot ===== |
| |
| </span><span class="kw">impl </span>Snapshot { |
| <span class="doccomment">/// Returns `true` if the task is in an idle state. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_idle(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& (RUNNING | COMPLETE) == <span class="number">0 |
| </span>} |
| |
| <span class="doccomment">/// Returns `true` if the task has been flagged as notified. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_notified(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& NOTIFIED == NOTIFIED |
| } |
| |
| <span class="kw">fn </span>unset_notified(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>&= !NOTIFIED |
| } |
| |
| <span class="kw">fn </span>set_notified(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= NOTIFIED |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_running(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& RUNNING == RUNNING |
| } |
| |
| <span class="kw">fn </span>set_running(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= RUNNING; |
| } |
| |
| <span class="kw">fn </span>unset_running(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>&= !RUNNING; |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_cancelled(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& CANCELLED == CANCELLED |
| } |
| |
| <span class="kw">fn </span>set_cancelled(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= CANCELLED; |
| } |
| |
| <span class="doccomment">/// Returns `true` if the task's future has completed execution. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_complete(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& COMPLETE == COMPLETE |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_join_interested(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& JOIN_INTEREST == JOIN_INTEREST |
| } |
| |
| <span class="kw">fn </span>unset_join_interested(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>&= !JOIN_INTEREST |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>is_join_waker_set(<span class="self">self</span>) -> bool { |
| <span class="self">self</span>.<span class="number">0 </span>& JOIN_WAKER == JOIN_WAKER |
| } |
| |
| <span class="kw">fn </span>set_join_waker(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>|= JOIN_WAKER; |
| } |
| |
| <span class="kw">fn </span>unset_join_waker(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.<span class="number">0 </span>&= !JOIN_WAKER |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ref_count(<span class="self">self</span>) -> usize { |
| (<span class="self">self</span>.<span class="number">0 </span>& REF_COUNT_MASK) >> REF_COUNT_SHIFT |
| } |
| |
| <span class="kw">fn </span>ref_inc(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="macro">assert!</span>(<span class="self">self</span>.<span class="number">0 </span><= isize::MAX <span class="kw">as </span>usize); |
| <span class="self">self</span>.<span class="number">0 </span>+= REF_ONE; |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ref_dec(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="macro">assert!</span>(<span class="self">self</span>.ref_count() > <span class="number">0</span>); |
| <span class="self">self</span>.<span class="number">0 </span>-= REF_ONE |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>State { |
| <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="kw">let </span>snapshot = <span class="self">self</span>.load(); |
| snapshot.fmt(fmt) |
| } |
| } |
| |
| <span class="kw">impl </span>fmt::Debug <span class="kw">for </span>Snapshot { |
| <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">"Snapshot"</span>) |
| .field(<span class="string">"is_running"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_running()) |
| .field(<span class="string">"is_complete"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_complete()) |
| .field(<span class="string">"is_notified"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_notified()) |
| .field(<span class="string">"is_cancelled"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_cancelled()) |
| .field(<span class="string">"is_join_interested"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_join_interested()) |
| .field(<span class="string">"is_join_waker_set"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_join_waker_set()) |
| .field(<span class="string">"ref_count"</span>, <span class="kw-2">&</span><span class="self">self</span>.ref_count()) |
| .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> |
