Fix races using resources on Close

client.go

@@ -422,26 +422,23 @@ func (cl *Client) eachDhtServer(f func(DhtServer)) {
 	}
 }
 
-// Stops the client. All connections to peers are closed and all activity will
-// come to a halt.
+// Stops the client. All connections to peers are closed and all activity will come to a halt.
 func (cl *Client) Close() (errs []error) {
-	cl.closed.Set()
 	var closeGroup sync.WaitGroup // For concurrent cleanup to complete before returning
 	cl.lock()
-	cl.event.Broadcast()
 	for _, t := range cl.torrents {
 		err := t.close(&closeGroup)
 		if err != nil {
 			errs = append(errs, err)
 		}
 	}
-	cl.unlock()
-	closeGroup.Wait() // defer is LIFO. We want to Wait() after cl.unlock()
-	cl.lock()
 	for i := range cl.onClose {
 		cl.onClose[len(cl.onClose)-1-i]()
 	}
+	cl.closed.Set()
 	cl.unlock()
+	cl.event.Broadcast()
+	closeGroup.Wait() // defer is LIFO. We want to Wait() after cl.unlock()
 	return
 }
 

tracker_scraper.go

@@ -81,6 +81,12 @@ func (me *trackerScraper) getIp() (ip net.IP, err error) {
 		err = errors.New("no ips")
 		return
 	}
+	me.t.cl.rLock()
+	defer me.t.cl.rUnlock()
+	if me.t.cl.closed.IsSet() {
+		err = errors.New("client is closed")
+		return
+	}
 	for _, ip = range ips {
 		if me.t.cl.ipIsBlocked(ip) {
 			continue