<!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 `/home/sangenya/.cargo/registry/src/github.com-1ecc6299db9ec823/rayon-core-1.9.1/src/latch.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>latch.rs - source</title><link rel="stylesheet" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><link rel="stylesheet" type="text/css" href="../../dark.css" disabled ><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled ><script id="default-settings"></script><script src="../../storage.js"></script><script src="../../crates.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="icon" type="image/svg+xml" href="../../favicon.svg">
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</pre><pre class="rust">
<span class="kw">use</span> <span class="ident">std::sync::atomic</span>::{<span class="ident">AtomicUsize</span>, <span class="ident">Ordering</span>};
<span class="kw">use</span> <span class="ident">std::sync</span>::{<span class="ident">Arc</span>, <span class="ident">Condvar</span>, <span class="ident">Mutex</span>};
<span class="kw">use</span> <span class="ident">std::usize</span>;
<span class="kw">use</span> <span class="kw">crate</span><span class="ident">::registry</span>::{<span class="ident">Registry</span>, <span class="ident">WorkerThread</span>};
<span class="doccomment">/// We define various kinds of latches, which are all a primitive signaling</span>
<span class="doccomment">/// mechanism. A latch starts as false. Eventually someone calls `set()` and</span>
<span class="doccomment">/// it becomes true. You can test if it has been set by calling `probe()`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Some kinds of latches, but not all, support a `wait()` operation</span>
<span class="doccomment">/// that will wait until the latch is set, blocking efficiently. That</span>
<span class="doccomment">/// is not part of the trait since it is not possibly to do with all</span>
<span class="doccomment">/// latches.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The intention is that `set()` is called once, but `probe()` may be</span>
<span class="doccomment">/// called any number of times. Once `probe()` returns true, the memory</span>
<span class="doccomment">/// effects that occurred before `set()` become visible.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// It'd probably be better to refactor the API into two paired types,</span>
<span class="doccomment">/// but that's a bit of work, and this is not a public API.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ## Memory ordering</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Latches need to guarantee two things:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - Once `probe()` returns true, all memory effects from the `set()`</span>
<span class="doccomment">/// are visible (in other words, the set should synchronize-with</span>
<span class="doccomment">/// the probe).</span>
<span class="doccomment">/// - Once `set()` occurs, the next `probe()` *will* observe it. This</span>
<span class="doccomment">/// typically requires a seq-cst ordering. See [the "tickle-then-get-sleepy" scenario in the sleep</span>
<span class="doccomment">/// README](/src/sleep/README.md#tickle-then-get-sleepy) for details.</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">trait</span> <span class="ident">Latch</span> {
<span class="doccomment">/// Set the latch, signalling others.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # WARNING</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Setting a latch triggers other threads to wake up and (in some</span>
<span class="doccomment">/// cases) complete. This may, in turn, cause memory to be</span>
<span class="doccomment">/// allocated and so forth. One must be very careful about this,</span>
<span class="doccomment">/// and it's typically better to read all the fields you will need</span>
<span class="doccomment">/// to access *before* a latch is set!</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>);
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">trait</span> <span class="ident">AsCoreLatch</span> {
<span class="kw">fn</span> <span class="ident">as_core_latch</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">&</span><span class="ident">CoreLatch</span>;
}
<span class="doccomment">/// Latch is not set, owning thread is awake</span>
<span class="kw">const</span> <span class="ident">UNSET</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">0</span>;
<span class="doccomment">/// Latch is not set, owning thread is going to sleep on this latch</span>
<span class="doccomment">/// (but has not yet fallen asleep).</span>
<span class="kw">const</span> <span class="ident">SLEEPY</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">1</span>;
<span class="doccomment">/// Latch is not set, owning thread is asleep on this latch and</span>
<span class="doccomment">/// must be awoken.</span>
<span class="kw">const</span> <span class="ident">SLEEPING</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">2</span>;
<span class="doccomment">/// Latch is set.</span>
<span class="kw">const</span> <span class="ident">SET</span>: <span class="ident">usize</span> <span class="op">=</span> <span class="number">3</span>;
<span class="doccomment">/// Spin latches are the simplest, most efficient kind, but they do</span>
<span class="doccomment">/// not support a `wait()` operation. They just have a boolean flag</span>
<span class="doccomment">/// that becomes true when `set()` is called.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct</span> <span class="ident">CoreLatch</span> {
<span class="ident">state</span>: <span class="ident">AtomicUsize</span>,
}
<span class="kw">impl</span> <span class="ident">CoreLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="self">Self</span> {
<span class="self">Self</span> {
<span class="ident">state</span>: <span class="ident">AtomicUsize::new</span>(<span class="number">0</span>),
}
}
<span class="doccomment">/// Returns the address of this core latch as an integer. Used</span>
<span class="doccomment">/// for logging.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">addr</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">usize</span> {
<span class="self">self</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">CoreLatch</span> <span class="kw">as</span> <span class="ident">usize</span>
}
<span class="doccomment">/// Invoked by owning thread as it prepares to sleep. Returns true</span>
<span class="doccomment">/// if the owning thread may proceed to fall asleep, false if the</span>
<span class="doccomment">/// latch was set in the meantime.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">get_sleepy</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">state</span>
.<span class="ident">compare_exchange</span>(<span class="ident">UNSET</span>, <span class="ident">SLEEPY</span>, <span class="ident">Ordering::SeqCst</span>, <span class="ident">Ordering::Relaxed</span>)
.<span class="ident">is_ok</span>()
}
<span class="doccomment">/// Invoked by owning thread as it falls asleep sleep. Returns</span>
<span class="doccomment">/// true if the owning thread should block, or false if the latch</span>
<span class="doccomment">/// was set in the meantime.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">fall_asleep</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">state</span>
.<span class="ident">compare_exchange</span>(<span class="ident">SLEEPY</span>, <span class="ident">SLEEPING</span>, <span class="ident">Ordering::SeqCst</span>, <span class="ident">Ordering::Relaxed</span>)
.<span class="ident">is_ok</span>()
}
<span class="doccomment">/// Invoked by owning thread as it falls asleep sleep. Returns</span>
<span class="doccomment">/// true if the owning thread should block, or false if the latch</span>
<span class="doccomment">/// was set in the meantime.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">wake_up</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">probe</span>() {
<span class="kw">let</span> <span class="kw">_</span> <span class="op">=</span>
<span class="self">self</span>.<span class="ident">state</span>
.<span class="ident">compare_exchange</span>(<span class="ident">SLEEPING</span>, <span class="ident">UNSET</span>, <span class="ident">Ordering::SeqCst</span>, <span class="ident">Ordering::Relaxed</span>);
}
}
<span class="doccomment">/// Set the latch. If this returns true, the owning thread was sleeping</span>
<span class="doccomment">/// and must be awoken.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is private because, typically, setting a latch involves</span>
<span class="doccomment">/// doing some wakeups; those are encapsulated in the surrounding</span>
<span class="doccomment">/// latch code.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">let</span> <span class="ident">old_state</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">state</span>.<span class="ident">swap</span>(<span class="ident">SET</span>, <span class="ident">Ordering::AcqRel</span>);
<span class="ident">old_state</span> <span class="op">=</span><span class="op">=</span> <span class="ident">SLEEPING</span>
}
<span class="doccomment">/// Test if this latch has been set.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">probe</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">state</span>.<span class="ident">load</span>(<span class="ident">Ordering::Acquire</span>) <span class="op">=</span><span class="op">=</span> <span class="ident">SET</span>
}
}
<span class="doccomment">/// Spin latches are the simplest, most efficient kind, but they do</span>
<span class="doccomment">/// not support a `wait()` operation. They just have a boolean flag</span>
<span class="doccomment">/// that becomes true when `set()` is called.</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct</span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="ident">core_latch</span>: <span class="ident">CoreLatch</span>,
<span class="ident">registry</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">Registry</span><span class="op">></span>,
<span class="ident">target_worker_index</span>: <span class="ident">usize</span>,
<span class="ident">cross</span>: <span class="ident">bool</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="doccomment">/// Creates a new spin latch that is owned by `thread`. This means</span>
<span class="doccomment">/// that `thread` is the only thread that should be blocking on</span>
<span class="doccomment">/// this latch -- it also means that when the latch is set, we</span>
<span class="doccomment">/// will wake `thread` if it is sleeping.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">thread</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">WorkerThread</span>) <span class="op">-</span><span class="op">></span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="ident">SpinLatch</span> {
<span class="ident">core_latch</span>: <span class="ident">CoreLatch::new</span>(),
<span class="ident">registry</span>: <span class="ident">thread</span>.<span class="ident">registry</span>(),
<span class="ident">target_worker_index</span>: <span class="ident">thread</span>.<span class="ident">index</span>(),
<span class="ident">cross</span>: <span class="bool-val">false</span>,
}
}
<span class="doccomment">/// Creates a new spin latch for cross-threadpool blocking. Notably, we</span>
<span class="doccomment">/// need to make sure the registry is kept alive after setting, so we can</span>
<span class="doccomment">/// safely call the notification.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">cross</span>(<span class="ident">thread</span>: <span class="kw-2">&</span><span class="lifetime">'r</span> <span class="ident">WorkerThread</span>) <span class="op">-</span><span class="op">></span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="ident">SpinLatch</span> {
<span class="ident">cross</span>: <span class="bool-val">true</span>,
..<span class="ident">SpinLatch::new</span>(<span class="ident">thread</span>)
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">probe</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="self">self</span>.<span class="ident">core_latch</span>.<span class="ident">probe</span>()
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> <span class="ident">AsCoreLatch</span> <span class="kw">for</span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">as_core_latch</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">&</span><span class="ident">CoreLatch</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">core_latch</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> <span class="ident">Latch</span> <span class="kw">for</span> <span class="ident">SpinLatch</span><span class="op"><</span><span class="lifetime">'r</span><span class="op">></span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">cross_registry</span>;
<span class="kw">let</span> <span class="ident">registry</span> <span class="op">=</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">cross</span> {
<span class="comment">// Ensure the registry stays alive while we notify it.</span>
<span class="comment">// Otherwise, it would be possible that we set the spin</span>
<span class="comment">// latch and the other thread sees it and exits, causing</span>
<span class="comment">// the registry to be deallocated, all before we get a</span>
<span class="comment">// chance to invoke `registry.notify_worker_latch_is_set`.</span>
<span class="ident">cross_registry</span> <span class="op">=</span> <span class="ident">Arc::clone</span>(<span class="self">self</span>.<span class="ident">registry</span>);
<span class="kw-2">&</span><span class="ident">cross_registry</span>
} <span class="kw">else</span> {
<span class="comment">// If this is not a "cross-registry" spin-latch, then the</span>
<span class="comment">// thread which is performing `set` is itself ensuring</span>
<span class="comment">// that the registry stays alive.</span>
<span class="self">self</span>.<span class="ident">registry</span>
};
<span class="kw">let</span> <span class="ident">target_worker_index</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">target_worker_index</span>;
<span class="comment">// NOTE: Once we `set`, the target may proceed and invalidate `&self`!</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">core_latch</span>.<span class="ident">set</span>() {
<span class="comment">// Subtle: at this point, we can no longer read from</span>
<span class="comment">// `self`, because the thread owning this spin latch may</span>
<span class="comment">// have awoken and deallocated the latch. Therefore, we</span>
<span class="comment">// only use fields whose values we already read.</span>
<span class="ident">registry</span>.<span class="ident">notify_worker_latch_is_set</span>(<span class="ident">target_worker_index</span>);
}
}
}
<span class="doccomment">/// A Latch starts as false and eventually becomes true. You can block</span>
<span class="doccomment">/// until it becomes true.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct</span> <span class="ident">LockLatch</span> {
<span class="ident">m</span>: <span class="ident">Mutex</span><span class="op"><</span><span class="ident">bool</span><span class="op">></span>,
<span class="ident">v</span>: <span class="ident">Condvar</span>,
}
<span class="kw">impl</span> <span class="ident">LockLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="ident">LockLatch</span> {
<span class="ident">LockLatch</span> {
<span class="ident">m</span>: <span class="ident">Mutex::new</span>(<span class="bool-val">false</span>),
<span class="ident">v</span>: <span class="ident">Condvar::new</span>(),
}
}
<span class="doccomment">/// Block until latch is set, then resets this lock latch so it can be reused again.</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">wait_and_reset</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">while</span> <span class="op">!</span><span class="kw-2">*</span><span class="ident">guard</span> {
<span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">v</span>.<span class="ident">wait</span>(<span class="ident">guard</span>).<span class="ident">unwrap</span>();
}
<span class="kw-2">*</span><span class="ident">guard</span> <span class="op">=</span> <span class="bool-val">false</span>;
}
<span class="doccomment">/// Block until latch is set.</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">wait</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw">while</span> <span class="op">!</span><span class="kw-2">*</span><span class="ident">guard</span> {
<span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">v</span>.<span class="ident">wait</span>(<span class="ident">guard</span>).<span class="ident">unwrap</span>();
}
}
}
<span class="kw">impl</span> <span class="ident">Latch</span> <span class="kw">for</span> <span class="ident">LockLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">guard</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">m</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="kw-2">*</span><span class="ident">guard</span> <span class="op">=</span> <span class="bool-val">true</span>;
<span class="self">self</span>.<span class="ident">v</span>.<span class="ident">notify_all</span>();
}
}
<span class="doccomment">/// Counting latches are used to implement scopes. They track a</span>
<span class="doccomment">/// counter. Unlike other latches, calling `set()` does not</span>
<span class="doccomment">/// necessarily make the latch be considered `set()`; instead, it just</span>
<span class="doccomment">/// decrements the counter. The latch is only "set" (in the sense that</span>
<span class="doccomment">/// `probe()` returns true) once the counter reaches zero.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note: like a `SpinLatch`, count laches are always associated with</span>
<span class="doccomment">/// some registry that is probing them, which must be tickled when</span>
<span class="doccomment">/// they are set. *Unlike* a `SpinLatch`, they don't themselves hold a</span>
<span class="doccomment">/// reference to that registry. This is because in some cases the</span>
<span class="doccomment">/// registry owns the count-latch, and that would create a cycle. So a</span>
<span class="doccomment">/// `CountLatch` must be given a reference to its owning registry when</span>
<span class="doccomment">/// it is set. For this reason, it does not implement the `Latch`</span>
<span class="doccomment">/// trait (but it doesn't have to, as it is not used in those generic</span>
<span class="doccomment">/// contexts).</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct</span> <span class="ident">CountLatch</span> {
<span class="ident">core_latch</span>: <span class="ident">CoreLatch</span>,
<span class="ident">counter</span>: <span class="ident">AtomicUsize</span>,
}
<span class="kw">impl</span> <span class="ident">CountLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="ident">CountLatch</span> {
<span class="ident">CountLatch</span> {
<span class="ident">core_latch</span>: <span class="ident">CoreLatch::new</span>(),
<span class="ident">counter</span>: <span class="ident">AtomicUsize::new</span>(<span class="number">1</span>),
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">increment</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="macro">debug_assert!</span>(<span class="op">!</span><span class="self">self</span>.<span class="ident">core_latch</span>.<span class="ident">probe</span>());
<span class="self">self</span>.<span class="ident">counter</span>.<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">Ordering::Relaxed</span>);
}
<span class="doccomment">/// Decrements the latch counter by one. If this is the final</span>
<span class="doccomment">/// count, then the latch is **set**, and calls to `probe()` will</span>
<span class="doccomment">/// return true. Returns whether the latch was set.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">counter</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Ordering::SeqCst</span>) <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
<span class="self">self</span>.<span class="ident">core_latch</span>.<span class="ident">set</span>();
<span class="bool-val">true</span>
} <span class="kw">else</span> {
<span class="bool-val">false</span>
}
}
<span class="doccomment">/// Decrements the latch counter by one and possibly set it. If</span>
<span class="doccomment">/// the latch is set, then the specific worker thread is tickled,</span>
<span class="doccomment">/// which should be the one that owns this latch.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">set_and_tickle_one</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">registry</span>: <span class="kw-2">&</span><span class="ident">Registry</span>, <span class="ident">target_worker_index</span>: <span class="ident">usize</span>) {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">set</span>() {
<span class="ident">registry</span>.<span class="ident">notify_worker_latch_is_set</span>(<span class="ident">target_worker_index</span>);
}
}
}
<span class="kw">impl</span> <span class="ident">AsCoreLatch</span> <span class="kw">for</span> <span class="ident">CountLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">as_core_latch</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">&</span><span class="ident">CoreLatch</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">core_latch</span>
}
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct</span> <span class="ident">CountLockLatch</span> {
<span class="ident">lock_latch</span>: <span class="ident">LockLatch</span>,
<span class="ident">counter</span>: <span class="ident">AtomicUsize</span>,
}
<span class="kw">impl</span> <span class="ident">CountLockLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-</span><span class="op">></span> <span class="ident">CountLockLatch</span> {
<span class="ident">CountLockLatch</span> {
<span class="ident">lock_latch</span>: <span class="ident">LockLatch::new</span>(),
<span class="ident">counter</span>: <span class="ident">AtomicUsize::new</span>(<span class="number">1</span>),
}
}
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">increment</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">old_counter</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">counter</span>.<span class="ident">fetch_add</span>(<span class="number">1</span>, <span class="ident">Ordering::Relaxed</span>);
<span class="macro">debug_assert!</span>(<span class="ident">old_counter</span> <span class="op">!</span><span class="op">=</span> <span class="number">0</span>);
}
<span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn</span> <span class="ident">wait</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="self">self</span>.<span class="ident">lock_latch</span>.<span class="ident">wait</span>();
}
}
<span class="kw">impl</span> <span class="ident">Latch</span> <span class="kw">for</span> <span class="ident">CountLockLatch</span> {
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">counter</span>.<span class="ident">fetch_sub</span>(<span class="number">1</span>, <span class="ident">Ordering::SeqCst</span>) <span class="op">=</span><span class="op">=</span> <span class="number">1</span> {
<span class="self">self</span>.<span class="ident">lock_latch</span>.<span class="ident">set</span>();
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">L</span><span class="op">></span> <span class="ident">Latch</span> <span class="kw">for</span> <span class="kw-2">&</span><span class="lifetime">'a</span> <span class="ident">L</span>
<span class="kw">where</span>
<span class="ident">L</span>: <span class="ident">Latch</span>,
{
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>) {
<span class="ident">L::set</span>(<span class="self">self</span>);
}
}
</pre></div>
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