[R4R]fix prefetcher related bugs (#491)

* fix goroutine leak in prefetcher

Signed-off-by: Keefe-Liu <bianze.kernel@gmail.com>

* wait all goroutine done to avoid prefetcher close panic

Signed-off-by: Keefe-Liu <bianze.kernel@gmail.com>

core/block_validator.go

@@ -144,13 +144,15 @@ func (v *BlockValidator) ValidateState(block *types.Block, statedb *state.StateD
  validateRes <- tmpFunc()
  }()
  }
+
+ var err error
  for i := 0; i < len(validateFuns); i++ {
  r := <-validateRes
- if r != nil {
- return r
+ if r != nil && err == nil {
+ err = r
  }
  }
- return nil
+ return err
 }
 
 // CalcGasLimit computes the gas limit of the next block after parent. It aims

core/state/statedb.go

@@ -958,6 +958,7 @@ func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 // goes into transaction receipts.
 func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
  if s.lightProcessed {
+ s.StopPrefetcher()
  return s.trie.Hash()
  }
  // Finalise all the dirty storage states and write them into the tries