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remove a race from the hashing write()

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Calling load() and store() separately leaves a lot of opportunity for a
race to occur.

This changes the logic to use compare_exchange() and will only return if
the previous value is absolutely not 1 at the point of comparison.

I also don't think this needs to be SeqCst, so relaxing that requirement
a little.
This commit is contained in:
Gary Pennington 2023-06-14 15:23:12 +01:00
parent 517f219066
commit 785be453f6
1 changed files with 11 additions and 8 deletions
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9
src/config/hashing.rs
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@ -50,9 +50,11 @@ impl HokmaLock {
pub fn write(&'static self) -> WhenTheHokmaSuppression { pub fn write(&'static self) -> WhenTheHokmaSuppression {
loop { loop {
let previous = self.lock.load(Ordering::SeqCst); // We are only interested in error results
self.lock.store(1, Ordering::SeqCst); if let Err(previous) = self
.lock
.compare_exchange(1, 1, Ordering::Acquire, Ordering::Relaxed)
{
if previous != 1 { if previous != 1 {
return WhenTheHokmaSuppression { return WhenTheHokmaSuppression {
hokma: self, hokma: self,
@ -62,6 +64,7 @@ impl HokmaLock {
} }
} }
} }
}
struct WhenTheHokmaSuppression { struct WhenTheHokmaSuppression {
hokma: &'static HokmaLock, hokma: &'static HokmaLock,