miner: fix concurrent map access in Miner.HashRate, close XFN-52 (#1634)

miner/miner.go

@@ -145,15 +145,7 @@ func (m *Miner) HashRate() (tot int64) {
 	if pow, ok := m.engine.(consensus.PoW); ok {
 		tot += int64(pow.Hashrate())
 	}
-	// do we care this might race? is it worth we're rewriting some
+	return tot + m.worker.getHashrate()
-	// aspects of the worker/locking up agents so we can get an accurate
-	// hashrate?
-	for agent := range m.worker.agents {
-		if _, ok := agent.(*CpuAgent); !ok {
-			tot += agent.GetHashRate()
-		}
-	}
-	return
 }
 
 func (m *Miner) SetExtra(extra []byte) error {

miner/worker.go

@@ -379,6 +379,19 @@ func (w *worker) update() {
 	}
 }
 
+func (w *worker) getHashrate() int64 {
+	w.mu.Lock()
+	defer w.mu.Unlock()
+
+	total := int64(0)
+	for agent := range w.agents {
+		if _, ok := agent.(*CpuAgent); !ok {
+			total += agent.GetHashRate()
+		}
+	}
+	return total
+}
+
 func getResetTime(chain *core.BlockChain, minePeriod int) time.Duration {
 	minePeriodDuration := time.Duration(minePeriod) * time.Second
 	currentBlockTime := int64(chain.CurrentBlock().Time())