updated godep ethash

Godeps/Godeps.json

@@ -22,8 +22,8 @@
 		},
 		{
 			"ImportPath": "github.com/ethereum/ethash",
-			"Comment": "v23-11-g5376ec8",
-			"Rev": "5376ec8816d6bf787d4fc91a08b4527bc5e1f469"
+			"Comment": "v23-12-g149261a",
+			"Rev": "149261a5d7cafc3943cbcf1d370082ec70d81e8b"
 		},
 		{
 			"ImportPath": "github.com/ethereum/serpent-go",

Godeps/_workspace/src/github.com/ethereum/ethash/ethash.go

@@ -102,7 +102,9 @@ func makeParamsAndCache(chainManager pow.ChainManager, blockNum uint64) (*Params
 
 func (pow *Ethash) UpdateCache(force bool) error {
 	pow.cacheMutex.Lock()
-	thisEpoch := pow.chainManager.CurrentBlock().NumberU64()
+	defer pow.cacheMutex.Unlock()
+
+	thisEpoch := pow.chainManager.CurrentBlock().NumberU64() / epochLength
 	if force || pow.paramsAndCache.Epoch != thisEpoch {
 		var err error
 		pow.paramsAndCache, err = makeParamsAndCache(pow.chainManager, pow.chainManager.CurrentBlock().NumberU64())
@@ -110,7 +112,7 @@ func (pow *Ethash) UpdateCache(force bool) error {
 			panic(err)
 		}
 	}
-	pow.cacheMutex.Unlock()
+
 	return nil
 }