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This commit is contained in:
John Kåre Alsaker 2023-09-02 01:22:22 +02:00
parent 25884ec9be
commit 50f0d666d3
1 changed files with 4 additions and 1 deletions
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5
compiler/rustc_data_structures/src/sync/freeze.rs
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@ -9,6 +9,8 @@ use std::{
/// A type which allows mutation using a lock until /// A type which allows mutation using a lock until
/// the value is frozen and can be accessed lock-free. /// the value is frozen and can be accessed lock-free.
///
/// Unlike `RwLock`, it can be used to prevent mutation past a point.
#[derive(Default)] #[derive(Default)]
pub struct Freeze<T> { pub struct Freeze<T> {
data: UnsafeCell<T>, data: UnsafeCell<T>,
@ -46,6 +48,7 @@ impl<T> Freeze<T> {
#[track_caller] #[track_caller]
pub fn write(&self) -> FreezeWriteGuard<'_, T> { pub fn write(&self) -> FreezeWriteGuard<'_, T> {
let _lock_guard = self.lock.write(); let _lock_guard = self.lock.write();
// Use relaxed ordering since we're in the write lock.
assert!(!self.frozen.load(Ordering::Relaxed), "still mutable"); assert!(!self.frozen.load(Ordering::Relaxed), "still mutable");
FreezeWriteGuard { FreezeWriteGuard {
_lock_guard, _lock_guard,
@ -58,7 +61,7 @@ impl<T> Freeze<T> {
#[inline] #[inline]
pub fn freeze(&self) -> &T { pub fn freeze(&self) -> &T {
if !self.frozen.load(Ordering::Acquire) { if !self.frozen.load(Ordering::Acquire) {
// Get the lock to ensure no concurrent writes. // Get the lock to ensure no concurrent writes and that we release the latest write.
let _lock = self.lock.write(); let _lock = self.lock.write();
self.frozen.store(true, Ordering::Release); self.frozen.store(true, Ordering::Release);
} }