core/rawdb: fix leak of backoff timer (#87)

core/rawdb/freezer.go

@@ -70,10 +70,10 @@ const (
 // freezer is an memory mapped append-only database to store immutable chain data
 // into flat files:
 //
-// - The append only nature ensures that disk writes are minimized.
-// - The memory mapping ensures we can max out system memory for caching without
-//   reserving it for go-ethereum. This would also reduce the memory requirements
-//   of Geth, and thus also GC overhead.
+//   - The append only nature ensures that disk writes are minimized.
+//   - The memory mapping ensures we can max out system memory for caching without
+//     reserving it for go-ethereum. This would also reduce the memory requirements
+//     of Geth, and thus also GC overhead.
 type freezer struct {
 	// WARNING: The `frozen` field is accessed atomically. On 32 bit platforms, only
 	// 64-bit aligned fields can be atomic. The struct is guaranteed to be so aligned,
@@ -205,9 +205,9 @@ func (f *freezer) Ancient(kind string, number uint64) ([]byte, error) {
 
 // AncientRange retrieves multiple items in sequence, starting from the index 'start'.
 // It will return
-//  - at most 'max' items,
-//  - at least 1 item (even if exceeding the maxByteSize), but will otherwise
-//   return as many items as fit into maxByteSize.
+//   - at most 'max' items,
+//   - at least 1 item (even if exceeding the maxByteSize), but will otherwise
+//     return as many items as fit into maxByteSize.
 func (f *freezer) AncientRange(kind string, start, count, maxBytes uint64) ([][]byte, error) {
 	if table := f.tables[kind]; table != nil {
 		return table.RetrieveItems(start, count, maxBytes)
@@ -339,6 +339,8 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 		backoff   bool
 		triggered chan struct{} // Used in tests
 	)
+	timer := time.NewTimer(freezerRecheckInterval)
+	defer timer.Stop()
 	for {
 		select {
 		case <-f.quit:
@@ -353,8 +355,9 @@ func (f *freezer) freeze(db ethdb.KeyValueStore) {
 				triggered = nil
 			}
 			select {
-			case <-time.NewTimer(freezerRecheckInterval).C:
+			case <-timer.C:
 				backoff = false
+				timer.Reset(freezerRecheckInterval)
 			case triggered = <-f.trigger:
 				backoff = false
 			case <-f.quit: