4lDO2
59 lines
1.3 KiB
Rust
59 lines
1.3 KiB
Rust
// TODO: Share code for simple futex-based mutex between relibc's Mutex<()> and this.
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use core::{
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cell::UnsafeCell,
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ops::{Deref, DerefMut},
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sync::atomic::{AtomicU32, Ordering},
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};
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pub struct Mutex<T> {
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pub lockword: AtomicU32,
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pub inner: UnsafeCell<T>,
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}
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const UNLOCKED: u32 = 0;
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const LOCKED: u32 = 1;
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const WAITING: u32 = 2;
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unsafe impl<T: Send> Send for Mutex<T> {}
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unsafe impl<T: Send> Sync for Mutex<T> {}
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impl<T> Mutex<T> {
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pub const fn new(t: T) -> Self {
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Self {
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lockword: AtomicU32::new(0),
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inner: UnsafeCell::new(t),
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}
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}
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pub fn lock(&self) -> MutexGuard<'_, T> {
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while self
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.lockword
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.compare_exchange(UNLOCKED, LOCKED, Ordering::Acquire, Ordering::Relaxed)
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.is_err()
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{
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core::hint::spin_loop();
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}
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MutexGuard { lock: self }
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}
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}
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pub struct MutexGuard<'l, T> {
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lock: &'l Mutex<T>,
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}
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impl<T> Deref for MutexGuard<'_, T> {
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type Target = T;
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fn deref(&self) -> &T {
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unsafe { &*self.lock.inner.get() }
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}
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}
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impl<T> DerefMut for MutexGuard<'_, T> {
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fn deref_mut(&mut self) -> &mut T {
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unsafe { &mut *self.lock.inner.get() }
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}
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}
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impl<T> Drop for MutexGuard<'_, T> {
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fn drop(&mut self) {
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self.lock.lockword.store(UNLOCKED, Ordering::Release);
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}
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}
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