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fix(FiFoQueues): Prevent evict race condition updating weights #769

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fix(FiFoQueues): Prevent evict race condition updating weights #769

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8 changes: 4 additions & 4 deletions tinyufo/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,11 +215,11 @@ impl<T: Clone + Send + Sync + 'static> FiFoQueues<T> {
};
let old = buckets.insert(key, bucket);
if old.is_none() {
// Always push key first before updating weight
// If doing the other order, another concurrent thread might not
// find things to evict
self.small.push(key);
// Always updating weight's before push key
// another concurrent thread might evict it before we add weight's
// risking an usize underflow
self.small_weight.fetch_add(weight as usize, SeqCst);
self.small.push(key);
} // else: two threads are racing adding the item
// TODO: compare old.weight and update accordingly
return evicted;
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