fix: ring buffer deadlock

internals/servicelog/ringbuffer.go

@@ -61,6 +61,8 @@ func NewRingBuffer(size int) *RingBuffer {
 func (rb *RingBuffer) Close() error {
 	rb.rwlock.Lock()
 	defer rb.rwlock.Unlock()
+	rb.iteratorMutex.Lock()
+	defer rb.iteratorMutex.Unlock()
 	if rb.writeClosed {
 		return nil
 	}
@@ -73,6 +75,10 @@ func (rb *RingBuffer) Close() error {
 func (rb *RingBuffer) Closed() bool {
 	rb.rwlock.RLock()
 	defer rb.rwlock.RUnlock()
+	return rb.closed()
+}
+
+func (rb *RingBuffer) closed() bool {
 	return rb.writeClosed
 }
 
@@ -158,6 +164,10 @@ func (rb *RingBuffer) Size() int {
 func (rb *RingBuffer) Positions() (start RingPos, end RingPos) {
 	rb.rwlock.RLock()
 	defer rb.rwlock.RUnlock()
+	return rb.positions()
+}
+
+func (rb *RingBuffer) positions() (start RingPos, end RingPos) {
 	return rb.readIndex, rb.writeIndex
 }
 
@@ -237,16 +247,18 @@ func (rb *RingBuffer) WriteTo(writer io.Writer, start RingPos) (next RingPos, n
 
 // TailIterator returns an iterator from the tail of the buffer.
 func (rb *RingBuffer) TailIterator() Iterator {
+	rb.rwlock.RLock()
+	defer rb.rwlock.RUnlock()
 	rb.iteratorMutex.Lock()
 	defer rb.iteratorMutex.Unlock()
-	start, _ := rb.Positions()
+	start, _ := rb.positions()
 	iter := &iterator{
 		rb:        rb,
 		index:     start,
 		nextChan:  make(chan bool, 1),
 		closeChan: make(chan struct{}),
 	}
-	if rb.Closed() {
+	if rb.closed() {
 		close(iter.closeChan)
 	}
 	rb.iteratorList = append(rb.iteratorList, iter)
@@ -258,6 +270,8 @@ func (rb *RingBuffer) TailIterator() Iterator {
 // backwards from the head.
 func (rb *RingBuffer) HeadIterator(lines int) Iterator {
 	firstLine := rb.reverseLinePosition(lines)
+	rb.rwlock.RLock()
+	defer rb.rwlock.RUnlock()
 	rb.iteratorMutex.Lock()
 	defer rb.iteratorMutex.Unlock()
 	iter := &iterator{
@@ -266,7 +280,7 @@ func (rb *RingBuffer) HeadIterator(lines int) Iterator {
 		nextChan:  make(chan bool, 1),
 		closeChan: make(chan struct{}),
 	}
-	if rb.Closed() {
+	if rb.closed() {
 		close(iter.closeChan)
 	}
 	rb.iteratorList = append(rb.iteratorList, iter)
@@ -339,8 +353,6 @@ func (rb *RingBuffer) signalIterators() {
 }
 
 func (rb *RingBuffer) releaseIterators() {
-	rb.iteratorMutex.Lock()
-	defer rb.iteratorMutex.Unlock()
 	for _, iter := range rb.iteratorList {
 		// Close closeChan if not already closed
 		select {