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<!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/io/scheduled_io.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>scheduled_io.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 super</span>::{ReadyEvent, Tick};
<span class="kw">use </span><span class="kw">crate</span>::io::interest::Interest;
<span class="kw">use </span><span class="kw">crate</span>::io::ready::Ready;
<span class="kw">use </span><span class="kw">crate</span>::loom::sync::atomic::AtomicUsize;
<span class="kw">use </span><span class="kw">crate</span>::loom::sync::Mutex;
<span class="kw">use </span><span class="kw">crate</span>::util::bit;
<span class="kw">use </span><span class="kw">crate</span>::util::slab::Entry;
<span class="kw">use </span><span class="kw">crate</span>::util::WakeList;
<span class="kw">use </span>std::sync::atomic::Ordering::{AcqRel, Acquire, Release};
<span class="kw">use </span>std::task::{Context, Poll, Waker};
<span class="kw">use </span><span class="kw">super</span>::Direction;
<span class="macro">cfg_io_readiness! </span>{
<span class="kw">use </span><span class="kw">crate</span>::util::linked_list::{<span class="self">self</span>, LinkedList};
<span class="kw">use </span>std::cell::UnsafeCell;
<span class="kw">use </span>std::future::Future;
<span class="kw">use </span>std::marker::PhantomPinned;
<span class="kw">use </span>std::pin::Pin;
<span class="kw">use </span>std::ptr::NonNull;
}
<span class="doccomment">/// Stored in the I/O driver resource slab.
</span><span class="attribute">#[derive(Debug)]
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>ScheduledIo {
<span class="doccomment">/// Packs the resource&#39;s readiness with the resource&#39;s generation.
</span>readiness: AtomicUsize,
waiters: Mutex&lt;Waiters&gt;,
}
<span class="macro">cfg_io_readiness! </span>{
<span class="kw">type </span>WaitList = LinkedList&lt;Waiter, &lt;Waiter <span class="kw">as </span>linked_list::Link&gt;::Target&gt;;
}
<span class="attribute">#[derive(Debug, Default)]
</span><span class="kw">struct </span>Waiters {
<span class="attribute">#[cfg(feature = <span class="string">&quot;net&quot;</span>)]
</span><span class="doccomment">/// List of all current waiters.
</span>list: WaitList,
<span class="doccomment">/// Waker used for AsyncRead.
</span>reader: <span class="prelude-ty">Option</span>&lt;Waker&gt;,
<span class="doccomment">/// Waker used for AsyncWrite.
</span>writer: <span class="prelude-ty">Option</span>&lt;Waker&gt;,
}
<span class="macro">cfg_io_readiness! </span>{
<span class="attribute">#[derive(Debug)]
</span><span class="kw">struct </span>Waiter {
pointers: linked_list::Pointers&lt;Waiter&gt;,
<span class="doccomment">/// The waker for this task.
</span>waker: <span class="prelude-ty">Option</span>&lt;Waker&gt;,
<span class="doccomment">/// The interest this waiter is waiting on.
</span>interest: Interest,
is_ready: bool,
<span class="doccomment">/// Should never be `!Unpin`.
</span>_p: PhantomPinned,
}
<span class="macro">generate_addr_of_methods! </span>{
<span class="kw">impl</span>&lt;&gt; Waiter {
<span class="kw">unsafe fn </span>addr_of_pointers(<span class="self">self</span>: NonNull&lt;<span class="self">Self</span>&gt;) -&gt; NonNull&lt;linked_list::Pointers&lt;Waiter&gt;&gt; {
<span class="kw-2">&amp;</span><span class="self">self</span>.pointers
}
}
}
<span class="doccomment">/// Future returned by `readiness()`.
</span><span class="kw">struct </span>Readiness&lt;<span class="lifetime">&#39;a</span>&gt; {
scheduled_io: <span class="kw-2">&amp;</span><span class="lifetime">&#39;a </span>ScheduledIo,
state: State,
<span class="doccomment">/// Entry in the waiter `LinkedList`.
</span>waiter: UnsafeCell&lt;Waiter&gt;,
}
<span class="kw">enum </span>State {
Init,
Waiting,
Done,
}
}
<span class="comment">// The `ScheduledIo::readiness` (`AtomicUsize`) is packed full of goodness.
//
// | shutdown | generation | driver tick | readiness |
// |----------+------------+--------------+-----------|
// | 1 bit | 7 bits + 8 bits + 16 bits |
</span><span class="kw">const </span>READINESS: bit::Pack = bit::Pack::least_significant(<span class="number">16</span>);
<span class="kw">const </span>TICK: bit::Pack = READINESS.then(<span class="number">8</span>);
<span class="kw">const </span>GENERATION: bit::Pack = TICK.then(<span class="number">7</span>);
<span class="kw">const </span>SHUTDOWN: bit::Pack = GENERATION.then(<span class="number">1</span>);
<span class="attribute">#[test]
</span><span class="kw">fn </span>test_generations_assert_same() {
<span class="macro">assert_eq!</span>(<span class="kw">super</span>::GENERATION, GENERATION);
}
<span class="comment">// ===== impl ScheduledIo =====
</span><span class="kw">impl </span>Entry <span class="kw">for </span>ScheduledIo {
<span class="kw">fn </span>reset(<span class="kw-2">&amp;</span><span class="self">self</span>) {
<span class="kw">let </span>state = <span class="self">self</span>.readiness.load(Acquire);
<span class="kw">let </span>generation = GENERATION.unpack(state);
<span class="kw">let </span>next = GENERATION.pack_lossy(generation + <span class="number">1</span>, <span class="number">0</span>);
<span class="self">self</span>.readiness.store(next, Release);
}
}
<span class="kw">impl </span>Default <span class="kw">for </span>ScheduledIo {
<span class="kw">fn </span>default() -&gt; ScheduledIo {
ScheduledIo {
readiness: AtomicUsize::new(<span class="number">0</span>),
waiters: Mutex::new(Default::default()),
}
}
}
<span class="kw">impl </span>ScheduledIo {
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>generation(<span class="kw-2">&amp;</span><span class="self">self</span>) -&gt; usize {
GENERATION.unpack(<span class="self">self</span>.readiness.load(Acquire))
}
<span class="doccomment">/// Invoked when the IO driver is shut down; forces this ScheduledIo into a
/// permanently shutdown state.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>shutdown(<span class="kw-2">&amp;</span><span class="self">self</span>) {
<span class="kw">let </span>mask = SHUTDOWN.pack(<span class="number">1</span>, <span class="number">0</span>);
<span class="self">self</span>.readiness.fetch_or(mask, AcqRel);
<span class="self">self</span>.wake(Ready::ALL);
}
<span class="doccomment">/// Sets the readiness on this `ScheduledIo` by invoking the given closure on
/// the current value, returning the previous readiness value.
///
/// # Arguments
/// - `token`: the token for this `ScheduledIo`.
/// - `tick`: whether setting the tick or trying to clear readiness for a
/// specific tick.
/// - `f`: a closure returning a new readiness value given the previous
/// readiness.
///
/// # Returns
///
/// If the given token&#39;s generation no longer matches the `ScheduledIo`&#39;s
/// generation, then the corresponding IO resource has been removed and
/// replaced with a new resource. In that case, this method returns `Err`.
/// Otherwise, this returns the previous readiness.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>set_readiness(
<span class="kw-2">&amp;</span><span class="self">self</span>,
token: <span class="prelude-ty">Option</span>&lt;usize&gt;,
tick: Tick,
f: <span class="kw">impl </span>Fn(Ready) -&gt; Ready,
) -&gt; <span class="prelude-ty">Result</span>&lt;(), ()&gt; {
<span class="kw">let </span><span class="kw-2">mut </span>current = <span class="self">self</span>.readiness.load(Acquire);
<span class="kw">loop </span>{
<span class="kw">let </span>current_generation = GENERATION.unpack(current);
<span class="kw">if let </span><span class="prelude-val">Some</span>(token) = token {
<span class="comment">// Check that the generation for this access is still the
// current one.
</span><span class="kw">if </span>GENERATION.unpack(token) != current_generation {
<span class="kw">return </span><span class="prelude-val">Err</span>(());
}
}
<span class="comment">// Mask out the tick/generation bits so that the modifying
// function doesn&#39;t see them.
</span><span class="kw">let </span>current_readiness = Ready::from_usize(current);
<span class="kw">let </span>new = f(current_readiness);
<span class="kw">let </span>packed = <span class="kw">match </span>tick {
Tick::Set(t) =&gt; TICK.pack(t <span class="kw">as </span>usize, new.as_usize()),
Tick::Clear(t) =&gt; {
<span class="kw">if </span>TICK.unpack(current) <span class="kw">as </span>u8 != t {
<span class="comment">// Trying to clear readiness with an old event!
</span><span class="kw">return </span><span class="prelude-val">Err</span>(());
}
TICK.pack(t <span class="kw">as </span>usize, new.as_usize())
}
};
<span class="kw">let </span>next = GENERATION.pack(current_generation, packed);
<span class="kw">match </span><span class="self">self
</span>.readiness
.compare_exchange(current, next, AcqRel, Acquire)
{
<span class="prelude-val">Ok</span>(<span class="kw">_</span>) =&gt; <span class="kw">return </span><span class="prelude-val">Ok</span>(()),
<span class="comment">// we lost the race, retry!
</span><span class="prelude-val">Err</span>(actual) =&gt; current = actual,
}
}
}
<span class="doccomment">/// Notifies all pending waiters that have registered interest in `ready`.
///
/// There may be many waiters to notify. Waking the pending task **must** be
/// done from outside of the lock otherwise there is a potential for a
/// deadlock.
///
/// A stack array of wakers is created and filled with wakers to notify, the
/// lock is released, and the wakers are notified. Because there may be more
/// than 32 wakers to notify, if the stack array fills up, the lock is
/// released, the array is cleared, and the iteration continues.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>wake(<span class="kw-2">&amp;</span><span class="self">self</span>, ready: Ready) {
<span class="kw">let </span><span class="kw-2">mut </span>wakers = WakeList::new();
<span class="kw">let </span><span class="kw-2">mut </span>waiters = <span class="self">self</span>.waiters.lock();
<span class="comment">// check for AsyncRead slot
</span><span class="kw">if </span>ready.is_readable() {
<span class="kw">if let </span><span class="prelude-val">Some</span>(waker) = waiters.reader.take() {
wakers.push(waker);
}
}
<span class="comment">// check for AsyncWrite slot
</span><span class="kw">if </span>ready.is_writable() {
<span class="kw">if let </span><span class="prelude-val">Some</span>(waker) = waiters.writer.take() {
wakers.push(waker);
}
}
<span class="attribute">#[cfg(feature = <span class="string">&quot;net&quot;</span>)]
</span><span class="lifetime">&#39;outer</span>: <span class="kw">loop </span>{
<span class="kw">let </span><span class="kw-2">mut </span>iter = waiters.list.drain_filter(|w| ready.satisfies(w.interest));
<span class="kw">while </span>wakers.can_push() {
<span class="kw">match </span>iter.next() {
<span class="prelude-val">Some</span>(waiter) =&gt; {
<span class="kw">let </span>waiter = <span class="kw">unsafe </span>{ <span class="kw-2">&amp;mut *</span>waiter.as_ptr() };
<span class="kw">if let </span><span class="prelude-val">Some</span>(waker) = waiter.waker.take() {
waiter.is_ready = <span class="bool-val">true</span>;
wakers.push(waker);
}
}
<span class="prelude-val">None </span>=&gt; {
<span class="kw">break </span><span class="lifetime">&#39;outer</span>;
}
}
}
drop(waiters);
wakers.wake_all();
<span class="comment">// Acquire the lock again.
</span>waiters = <span class="self">self</span>.waiters.lock();
}
<span class="comment">// Release the lock before notifying
</span>drop(waiters);
wakers.wake_all();
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>ready_event(<span class="kw-2">&amp;</span><span class="self">self</span>, interest: Interest) -&gt; ReadyEvent {
<span class="kw">let </span>curr = <span class="self">self</span>.readiness.load(Acquire);
ReadyEvent {
tick: TICK.unpack(curr) <span class="kw">as </span>u8,
ready: interest.mask() &amp; Ready::from_usize(READINESS.unpack(curr)),
is_shutdown: SHUTDOWN.unpack(curr) != <span class="number">0</span>,
}
}
<span class="doccomment">/// Polls for readiness events in a given direction.
///
/// These are to support `AsyncRead` and `AsyncWrite` polling methods,
/// which cannot use the `async fn` version. This uses reserved reader
/// and writer slots.
</span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>poll_readiness(
<span class="kw-2">&amp;</span><span class="self">self</span>,
cx: <span class="kw-2">&amp;mut </span>Context&lt;<span class="lifetime">&#39;_</span>&gt;,
direction: Direction,
) -&gt; Poll&lt;ReadyEvent&gt; {
<span class="kw">let </span>curr = <span class="self">self</span>.readiness.load(Acquire);
<span class="kw">let </span>ready = direction.mask() &amp; Ready::from_usize(READINESS.unpack(curr));
<span class="kw">let </span>is_shutdown = SHUTDOWN.unpack(curr) != <span class="number">0</span>;
<span class="kw">if </span>ready.is_empty() &amp;&amp; !is_shutdown {
<span class="comment">// Update the task info
</span><span class="kw">let </span><span class="kw-2">mut </span>waiters = <span class="self">self</span>.waiters.lock();
<span class="kw">let </span>slot = <span class="kw">match </span>direction {
Direction::Read =&gt; <span class="kw-2">&amp;mut </span>waiters.reader,
Direction::Write =&gt; <span class="kw-2">&amp;mut </span>waiters.writer,
};
<span class="comment">// Avoid cloning the waker if one is already stored that matches the
// current task.
</span><span class="kw">match </span>slot {
<span class="prelude-val">Some</span>(existing) =&gt; {
<span class="kw">if </span>!existing.will_wake(cx.waker()) {
<span class="kw-2">*</span>existing = cx.waker().clone();
}
}
<span class="prelude-val">None </span>=&gt; {
<span class="kw-2">*</span>slot = <span class="prelude-val">Some</span>(cx.waker().clone());
}
}
<span class="comment">// Try again, in case the readiness was changed while we were
// taking the waiters lock
</span><span class="kw">let </span>curr = <span class="self">self</span>.readiness.load(Acquire);
<span class="kw">let </span>ready = direction.mask() &amp; Ready::from_usize(READINESS.unpack(curr));
<span class="kw">let </span>is_shutdown = SHUTDOWN.unpack(curr) != <span class="number">0</span>;
<span class="kw">if </span>is_shutdown {
Poll::Ready(ReadyEvent {
tick: TICK.unpack(curr) <span class="kw">as </span>u8,
ready: direction.mask(),
is_shutdown,
})
} <span class="kw">else if </span>ready.is_empty() {
Poll::Pending
} <span class="kw">else </span>{
Poll::Ready(ReadyEvent {
tick: TICK.unpack(curr) <span class="kw">as </span>u8,
ready,
is_shutdown,
})
}
} <span class="kw">else </span>{
Poll::Ready(ReadyEvent {
tick: TICK.unpack(curr) <span class="kw">as </span>u8,
ready,
is_shutdown,
})
}
}
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>clear_readiness(<span class="kw-2">&amp;</span><span class="self">self</span>, event: ReadyEvent) {
<span class="comment">// This consumes the current readiness state **except** for closed
// states. Closed states are excluded because they are final states.
</span><span class="kw">let </span>mask_no_closed = event.ready - Ready::READ_CLOSED - Ready::WRITE_CLOSED;
<span class="comment">// result isn&#39;t important
</span><span class="kw">let _ </span>= <span class="self">self</span>.set_readiness(<span class="prelude-val">None</span>, Tick::Clear(event.tick), |curr| curr - mask_no_closed);
}
<span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>clear_wakers(<span class="kw-2">&amp;</span><span class="self">self</span>) {
<span class="kw">let </span><span class="kw-2">mut </span>waiters = <span class="self">self</span>.waiters.lock();
waiters.reader.take();
waiters.writer.take();
}
}
<span class="kw">impl </span>Drop <span class="kw">for </span>ScheduledIo {
<span class="kw">fn </span>drop(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
<span class="self">self</span>.wake(Ready::ALL);
}
}
<span class="kw">unsafe impl </span>Send <span class="kw">for </span>ScheduledIo {}
<span class="kw">unsafe impl </span>Sync <span class="kw">for </span>ScheduledIo {}
<span class="macro">cfg_io_readiness! </span>{
<span class="kw">impl </span>ScheduledIo {
<span class="doccomment">/// An async version of `poll_readiness` which uses a linked list of wakers.
</span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">async fn </span>readiness(<span class="kw-2">&amp;</span><span class="self">self</span>, interest: Interest) -&gt; ReadyEvent {
<span class="self">self</span>.readiness_fut(interest).<span class="kw">await
</span>}
<span class="comment">// This is in a separate function so that the borrow checker doesn&#39;t think
// we are borrowing the `UnsafeCell` possibly over await boundaries.
//
// Go figure.
</span><span class="kw">fn </span>readiness_fut(<span class="kw-2">&amp;</span><span class="self">self</span>, interest: Interest) -&gt; Readiness&lt;<span class="lifetime">&#39;_</span>&gt; {
Readiness {
scheduled_io: <span class="self">self</span>,
state: State::Init,
waiter: UnsafeCell::new(Waiter {
pointers: linked_list::Pointers::new(),
waker: <span class="prelude-val">None</span>,
is_ready: <span class="bool-val">false</span>,
interest,
_p: PhantomPinned,
}),
}
}
}
<span class="kw">unsafe impl </span>linked_list::Link <span class="kw">for </span>Waiter {
<span class="kw">type </span>Handle = NonNull&lt;Waiter&gt;;
<span class="kw">type </span>Target = Waiter;
<span class="kw">fn </span>as_raw(handle: <span class="kw-2">&amp;</span>NonNull&lt;Waiter&gt;) -&gt; NonNull&lt;Waiter&gt; {
<span class="kw-2">*</span>handle
}
<span class="kw">unsafe fn </span>from_raw(ptr: NonNull&lt;Waiter&gt;) -&gt; NonNull&lt;Waiter&gt; {
ptr
}
<span class="kw">unsafe fn </span>pointers(target: NonNull&lt;Waiter&gt;) -&gt; NonNull&lt;linked_list::Pointers&lt;Waiter&gt;&gt; {
Waiter::addr_of_pointers(target)
}
}
<span class="comment">// ===== impl Readiness =====
</span><span class="kw">impl </span>Future <span class="kw">for </span>Readiness&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">type </span>Output = ReadyEvent;
<span class="kw">fn </span>poll(<span class="self">self</span>: Pin&lt;<span class="kw-2">&amp;mut </span><span class="self">Self</span>&gt;, cx: <span class="kw-2">&amp;mut </span>Context&lt;<span class="lifetime">&#39;_</span>&gt;) -&gt; Poll&lt;<span class="self">Self</span>::Output&gt; {
<span class="kw">use </span>std::sync::atomic::Ordering::SeqCst;
<span class="kw">let </span>(scheduled_io, state, waiter) = <span class="kw">unsafe </span>{
<span class="kw">let </span>me = <span class="self">self</span>.get_unchecked_mut();
(<span class="kw-2">&amp;</span>me.scheduled_io, <span class="kw-2">&amp;mut </span>me.state, <span class="kw-2">&amp;</span>me.waiter)
};
<span class="kw">loop </span>{
<span class="kw">match </span><span class="kw-2">*</span>state {
State::Init =&gt; {
<span class="comment">// Optimistically check existing readiness
</span><span class="kw">let </span>curr = scheduled_io.readiness.load(SeqCst);
<span class="kw">let </span>ready = Ready::from_usize(READINESS.unpack(curr));
<span class="kw">let </span>is_shutdown = SHUTDOWN.unpack(curr) != <span class="number">0</span>;
<span class="comment">// Safety: `waiter.interest` never changes
</span><span class="kw">let </span>interest = <span class="kw">unsafe </span>{ (<span class="kw-2">*</span>waiter.get()).interest };
<span class="kw">let </span>ready = ready.intersection(interest);
<span class="kw">if </span>!ready.is_empty() || is_shutdown {
<span class="comment">// Currently ready!
</span><span class="kw">let </span>tick = TICK.unpack(curr) <span class="kw">as </span>u8;
<span class="kw-2">*</span>state = State::Done;
<span class="kw">return </span>Poll::Ready(ReadyEvent { tick, ready, is_shutdown });
}
<span class="comment">// Wasn&#39;t ready, take the lock (and check again while locked).
</span><span class="kw">let </span><span class="kw-2">mut </span>waiters = scheduled_io.waiters.lock();
<span class="kw">let </span>curr = scheduled_io.readiness.load(SeqCst);
<span class="kw">let </span><span class="kw-2">mut </span>ready = Ready::from_usize(READINESS.unpack(curr));
<span class="kw">let </span>is_shutdown = SHUTDOWN.unpack(curr) != <span class="number">0</span>;
<span class="kw">if </span>is_shutdown {
ready = Ready::ALL;
}
<span class="kw">let </span>ready = ready.intersection(interest);
<span class="kw">if </span>!ready.is_empty() || is_shutdown {
<span class="comment">// Currently ready!
</span><span class="kw">let </span>tick = TICK.unpack(curr) <span class="kw">as </span>u8;
<span class="kw-2">*</span>state = State::Done;
<span class="kw">return </span>Poll::Ready(ReadyEvent { tick, ready, is_shutdown });
}
<span class="comment">// Not ready even after locked, insert into list...
// Safety: called while locked
</span><span class="kw">unsafe </span>{
(<span class="kw-2">*</span>waiter.get()).waker = <span class="prelude-val">Some</span>(cx.waker().clone());
}
<span class="comment">// Insert the waiter into the linked list
//
// safety: pointers from `UnsafeCell` are never null.
</span>waiters
.list
.push_front(<span class="kw">unsafe </span>{ NonNull::new_unchecked(waiter.get()) });
<span class="kw-2">*</span>state = State::Waiting;
}
State::Waiting =&gt; {
<span class="comment">// Currently in the &quot;Waiting&quot; state, implying the caller has
// a waiter stored in the waiter list (guarded by
// `notify.waiters`). In order to access the waker fields,
// we must hold the lock.
</span><span class="kw">let </span>waiters = scheduled_io.waiters.lock();
<span class="comment">// Safety: called while locked
</span><span class="kw">let </span>w = <span class="kw">unsafe </span>{ <span class="kw-2">&amp;mut *</span>waiter.get() };
<span class="kw">if </span>w.is_ready {
<span class="comment">// Our waker has been notified.
</span><span class="kw-2">*</span>state = State::Done;
} <span class="kw">else </span>{
<span class="comment">// Update the waker, if necessary.
</span><span class="kw">if </span>!w.waker.as_ref().unwrap().will_wake(cx.waker()) {
w.waker = <span class="prelude-val">Some</span>(cx.waker().clone());
}
<span class="kw">return </span>Poll::Pending;
}
<span class="comment">// Explicit drop of the lock to indicate the scope that the
// lock is held. Because holding the lock is required to
// ensure safe access to fields not held within the lock, it
// is helpful to visualize the scope of the critical
// section.
</span>drop(waiters);
}
State::Done =&gt; {
<span class="comment">// Safety: State::Done means it is no longer shared
</span><span class="kw">let </span>w = <span class="kw">unsafe </span>{ <span class="kw-2">&amp;mut *</span>waiter.get() };
<span class="kw">let </span>curr = scheduled_io.readiness.load(Acquire);
<span class="kw">let </span>is_shutdown = SHUTDOWN.unpack(curr) != <span class="number">0</span>;
<span class="comment">// The returned tick might be newer than the event
// which notified our waker. This is ok because the future
// still didn&#39;t return `Poll::Ready`.
</span><span class="kw">let </span>tick = TICK.unpack(curr) <span class="kw">as </span>u8;
<span class="comment">// The readiness state could have been cleared in the meantime,
// but we allow the returned ready set to be empty.
</span><span class="kw">let </span>curr_ready = Ready::from_usize(READINESS.unpack(curr));
<span class="kw">let </span>ready = curr_ready.intersection(w.interest);
<span class="kw">return </span>Poll::Ready(ReadyEvent {
tick,
ready,
is_shutdown,
});
}
}
}
}
}
<span class="kw">impl </span>Drop <span class="kw">for </span>Readiness&lt;<span class="lifetime">&#39;_</span>&gt; {
<span class="kw">fn </span>drop(<span class="kw-2">&amp;mut </span><span class="self">self</span>) {
<span class="kw">let </span><span class="kw-2">mut </span>waiters = <span class="self">self</span>.scheduled_io.waiters.lock();
<span class="comment">// Safety: `waiter` is only ever stored in `waiters`
</span><span class="kw">unsafe </span>{
waiters
.list
.remove(NonNull::new_unchecked(<span class="self">self</span>.waiter.get()))
};
}
}
<span class="kw">unsafe impl </span>Send <span class="kw">for </span>Readiness&lt;<span class="lifetime">&#39;_</span>&gt; {}
<span class="kw">unsafe impl </span>Sync <span class="kw">for </span>Readiness&lt;<span class="lifetime">&#39;_</span>&gt; {}
}
</code></pre></div>
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