fix edge cases refCounter close channel twice

internal/utils/ref_count.go

@@ -24,11 +24,31 @@ func (rc *RefCount) Zero() <-chan struct{} {
 }
 
 func (rc *RefCount) Add() {
-	atomic.AddUint32(&rc.refCount, 1)
+	// We add before checking to ensure proper ordering
+	newV := atomic.AddUint32(&rc.refCount, 1)
+	if newV == 1 {
+		// If it was 0 before we added, that means we're incrementing after a close
+		// This is a programming error
+		panic("RefCount.Add() called after count reached zero")
+	}
 }
 
 func (rc *RefCount) Sub() {
-	if atomic.AddUint32(&rc.refCount, ^uint32(0)) == 0 {
-		close(rc.zeroCh)
+	// First read the current value
+	for {
+		current := atomic.LoadUint32(&rc.refCount)
+		if current == 0 {
+			// Already at zero, channel should be closed
+			return
+		}
+
+		// Try to decrement, but only if the value hasn't changed
+		if atomic.CompareAndSwapUint32(&rc.refCount, current, current-1) {
+			if current == 1 { // Was this the last reference?
+				close(rc.zeroCh)
+			}
+			return
+		}
+		// If CAS failed, someone else modified the count, try again
 	}
 }

internal/utils/ref_count_test.go

@@ -4,6 +4,8 @@ import (
 	"sync"
 	"testing"
 	"time"
+
+	. "github.com/yusing/go-proxy/internal/utils/testing"
 )
 
 func TestRefCounterAddSub(t *testing.T) {
@@ -12,18 +14,16 @@ func TestRefCounterAddSub(t *testing.T) {
 	var wg sync.WaitGroup
 	wg.Add(2)
 
-	go func() {
-		defer wg.Done()
-		rc.Add()
-	}()
-
-	go func() {
-		defer wg.Done()
-		rc.Sub()
-		rc.Sub()
-	}()
+	rc.Add()
+	for range 2 {
+		go func() {
+			defer wg.Done()
+			rc.Sub()
+		}()
+	}
 
 	wg.Wait()
+	ExpectEqual(t, int(rc.refCount), 0)
 
 	select {
 	case <-rc.Zero():
@@ -39,7 +39,7 @@ func TestRefCounterMultipleAddSub(t *testing.T) {
 	var wg sync.WaitGroup
 	numAdds := 5
 	numSubs := 5
-	wg.Add(numAdds + numSubs)
+	wg.Add(numAdds)
 
 	for range numAdds {
 		go func() {
@@ -47,17 +47,20 @@ func TestRefCounterMultipleAddSub(t *testing.T) {
 			rc.Add()
 		}()
 	}
+	wg.Wait()
+	ExpectEqual(t, int(rc.refCount), numAdds+1)
 
+	wg.Add(numSubs)
 	for range numSubs {
 		go func() {
 			defer wg.Done()
 			rc.Sub()
-			rc.Sub()
 		}()
 	}
-
 	wg.Wait()
+	ExpectEqual(t, int(rc.refCount), numAdds+1-numSubs)
 
+	rc.Sub()
 	select {
 	case <-rc.Zero():
 		// Expected behavior