59 lines
1.7 KiB
Rust
59 lines
1.7 KiB
Rust
use core::sync::atomic::{AtomicU32, Ordering};
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#[derive(Clone, Copy)]
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pub(crate) struct Token(());
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/// Creates a token and passes it to the closure.
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///
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/// This is a no-op replacement for `CriticalSection::with` because we don't need any locking.
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pub(crate) fn locked<R>(f: impl FnOnce(Token) -> R) -> R {
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f(Token(()))
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}
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/// Task is spawned (has a future)
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pub(crate) const STATE_SPAWNED: u32 = 1 << 0;
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/// Task is in the executor run queue
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pub(crate) const STATE_RUN_QUEUED: u32 = 1 << 1;
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pub(crate) struct State {
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state: AtomicU32,
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}
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impl State {
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pub const fn new() -> State {
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Self {
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state: AtomicU32::new(0),
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}
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}
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/// If task is idle, mark it as spawned + run_queued and return true.
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#[inline(always)]
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pub fn spawn(&self) -> bool {
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self.state
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.compare_exchange(0, STATE_SPAWNED | STATE_RUN_QUEUED, Ordering::AcqRel, Ordering::Acquire)
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.is_ok()
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}
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/// Unmark the task as spawned.
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#[inline(always)]
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pub fn despawn(&self) {
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self.state.fetch_and(!STATE_SPAWNED, Ordering::AcqRel);
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}
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/// Mark the task as run-queued if it's spawned and isn't already run-queued. Run the given
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/// function if the task was successfully marked.
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#[inline(always)]
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pub fn run_enqueue(&self, f: impl FnOnce(Token)) {
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let prev = self.state.fetch_or(STATE_RUN_QUEUED, Ordering::AcqRel);
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if prev & STATE_RUN_QUEUED == 0 {
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locked(f);
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}
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}
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/// Unmark the task as run-queued. Return whether the task is spawned.
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#[inline(always)]
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pub fn run_dequeue(&self) {
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self.state.fetch_and(!STATE_RUN_QUEUED, Ordering::AcqRel);
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}
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}
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