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Implement try_lock_weak for use in lock loop #4

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Merged
merged 1 commit into from Jul 6, 2020
Merged

Implement try_lock_weak for use in lock loop #4

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13 changes: 12 additions & 1 deletion src/spinlock.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,17 @@ pub struct RawSpinlock {
locked: AtomicBool,
}

impl RawSpinlock {
// Can fail to lock even if the spinlock is not locked. May be more efficient than `try_lock`
// when called in a loop.
fn try_lock_weak(&self) -> bool {
// The Orderings are the same as try_lock, and are still correct here.
self.locked
.compare_exchange_weak(false, true, Ordering::Acquire, Ordering::Relaxed)
.is_ok()
}
}

unsafe impl RawMutex for RawSpinlock {
const INIT: RawSpinlock = RawSpinlock {
locked: AtomicBool::new(false),
Expand All @@ -35,7 +46,7 @@ unsafe impl RawMutex for RawSpinlock {
type GuardMarker = GuardSend;

fn lock(&self) {
while !self.try_lock() {
while !self.try_lock_weak() {
// Wait until the lock looks unlocked before retrying
// Code from https://github.com/mvdnes/spin-rs/commit/d3e60d19adbde8c8e9d3199c7c51e51ee5a20bf6
//
Expand Down