address pr comments

Author: ndyakov

internal/auth/conn_reauth_credentials_listener.go

@@ -54,18 +54,27 @@ func (c *ConnReAuthCredentialsListener) OnNext(credentials auth2.Credentials) {
 		case <-timeout:
 			err = pool.ErrConnUnusableTimeout
 		default:
+			// small sleep to avoid busy looping
+			time.Sleep(100 * time.Microsecond)
+			// yield the thread to allow other goroutines to run
 			runtime.Gosched()
 		}
 	}
 	if err == nil {
 		defer c.conn.SetUsable(true)
 	}
 
+	// This check just verifies that the connection is not in use.
+	// If the connection is in use, we don't want to interfere with that.
+	// As soon as the connection is not in use, we mark it as in use.
 	for err == nil && !c.conn.Used.CompareAndSwap(false, true) {
 		select {
 		case <-timeout:
 			err = pool.ErrConnUnusableTimeout
 		default:
+			// small sleep to avoid busy looping
+			time.Sleep(100 * time.Microsecond)
+			// yield the thread to allow other goroutines to run
 			runtime.Gosched()
 		}
 	}

internal/pool/buffer_size_test.go

@@ -123,16 +123,19 @@ var _ = Describe("Buffer Size Configuration", func() {
 })
 
 // Helper functions to extract buffer sizes using unsafe pointers
-// The struct layout must match pool.Conn exactly to avoid checkptr violations
+// The struct layout must match pool.Conn exactly to avoid checkptr violations.
+// checkptr is Go's pointer safety checker, which ensures that unsafe pointer
+// conversions are valid. If the struct layouts do not match exactly, this can
+// cause runtime panics or incorrect memory access due to invalid pointer dereferencing.
 func getWriterBufSizeUnsafe(cn *pool.Conn) int {
 	// Import required for atomic types
 	type atomicBool struct{ _ uint32 }
 	type atomicInt64 struct{ _ int64 }
 
 	cnPtr := (*struct {
-		id            uint64        // First field in pool.Conn
-		usedAt        int64         // Second field (atomic)
-		netConnAtomic interface{}   // atomic.Value (interface{} has same size)
+		id            uint64      // First field in pool.Conn
+		usedAt        int64       // Second field (atomic)
+		netConnAtomic interface{} // atomic.Value (interface{} has same size)
 		rd            *proto.Reader
 		bw            *bufio.Writer
 		wr            *proto.Writer
@@ -156,9 +159,9 @@ func getWriterBufSizeUnsafe(cn *pool.Conn) int {
 
 func getReaderBufSizeUnsafe(cn *pool.Conn) int {
 	cnPtr := (*struct {
-		id            uint64        // First field in pool.Conn
-		usedAt        int64         // Second field (atomic)
-		netConnAtomic interface{}   // atomic.Value (interface{} has same size)
+		id            uint64      // First field in pool.Conn
+		usedAt        int64       // Second field (atomic)
+		netConnAtomic interface{} // atomic.Value (interface{} has same size)
 		rd            *proto.Reader
 		bw            *bufio.Writer
 		wr            *proto.Writer

internal/pool/conn.go

@@ -493,10 +493,13 @@ func (cn *Conn) MarkQueuedForHandoff() error {
 
 		// first we need to mark the connection as not usable
 		// to prevent the pool from returning it to the caller
-		if !connAcquired && !cn.Usable.CompareAndSwap(true, false) {
-			continue
+		if !connAcquired {
+			if cn.Usable.CompareAndSwap(true, false) {
+				connAcquired = true
+			} else {
+				continue
+			}
 		}
-		connAcquired = true
 
 		currentState := cn.getHandoffState()
 		// Check if marked for handoff

redis.go

@@ -319,7 +319,7 @@ func (c *baseClient) connReAuthCredentialsListener(poolCn *pool.Conn) (auth.Cred
 	// Design decision: The main case we expect the connection to be in a non-usable state is when it is being reconnected
 	// during a handoff from maintnotifications.
 	// Setting the checkUsableTimeout to the handoff timeout if maintnotifications are enabled
-	// the default timeout if no maintnotifications are disabled is going to PoolTimeout.
+	// the default timeout if maintnotifications are disabled is going to PoolTimeout.
 	//
 	// Note: Due to the auto by default mode of MaintNotificationsConfig
 	// the timeout for the first connection will probably be the value of MaintNotificationsConfig.HandoffTimeout