Fix another race condition.

cmd/outline-ss-server/lru_cache.go

@@ -49,22 +49,28 @@ func NewLRUCache[K comparable, V any](capacity int, duration time.Duration, clea
 
 func (c *LRUCache[K, V]) Get(key K) (V, bool) {
 	c.mu.RLock()
-	defer c.mu.RUnlock()
+	elem, ok := c.items[key]
+	if !ok {
+		c.mu.RUnlock()
+		var zero V
+		return zero, false
+	}
+	ent := elem.Value.(*entry[K, V])
+	c.mu.RUnlock()
 
-	if elem, ok := c.items[key]; ok {
-		c.lru.MoveToFront(elem)
-		ent := elem.Value.(*entry[K, V])
-		if time.Since(ent.lastAccess) > c.duration {
-			c.lru.Remove(elem)
-			delete(c.items, key)
-			var zero V
-			return zero, false
-		}
-		ent.lastAccess = time.Now()
-		return ent.value, true
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if time.Since(ent.lastAccess) > c.duration {
+		c.lru.Remove(elem)
+		delete(c.items, key)
+		var zero V
+		return zero, false
 	}
-	var zero V
-	return zero, false
+
+	c.lru.MoveToFront(elem)
+	ent.lastAccess = time.Now()
+	return ent.value, true
 }
 
 func (c *LRUCache[K, V]) Set(key K, value V) {

cmd/outline-ss-server/lru_cache_test.go

@@ -15,6 +15,8 @@
 package main
 
 import (
+	"math/rand"
+	"sync"
 	"testing"
 	"time"
 
@@ -76,3 +78,29 @@ func TestLRUCache(t *testing.T) {
 		cache.StopCleanup()
 	})
 }
+
+func BenchmarkLRUCache(b *testing.B) {
+	cache := NewLRUCache[int, int](1000, time.Minute, time.Minute)
+
+	keys := make([]int, b.N)
+	for i := 0; i < b.N; i++ {
+		keys[i] = rand.Intn(2000)
+	}
+
+	b.ResetTimer()
+
+	var wg sync.WaitGroup
+	for i := 0; i < b.N; i++ {
+		wg.Add(1)
+		go func(key int) {
+			defer wg.Done()
+			cache.Get(key)
+			if rand.Intn(2) == 0 {
+				cache.Set(key, rand.Int())
+			}
+		}(keys[i])
+	}
+	wg.Wait()
+
+	cache.StopCleanup()
+}