core/state/snapshot: port changes from 29995 (ethereum#30040)

ethereum#29995 has been reverted due to an unexpected flaw in the state snapshot
process.

Specifically, it attempts to stop the state snapshot generation, which
could potentially
cause the system to halt if the generation is not currently running.

This pull request ports the changes made in ethereum#29995 and fixes the flaw.

core/state/snapshot/disklayer.go

@@ -74,6 +74,14 @@ func (dl *diskLayer) Stale() bool {
 	return dl.stale
 }
 
+// markStale sets the stale flag as true.
+func (dl *diskLayer) markStale() {
+	dl.lock.Lock()
+	defer dl.lock.Unlock()
+
+	dl.stale = true
+}
+
 // Account directly retrieves the account associated with a particular hash in
 // the snapshot slim data format.
 func (dl *diskLayer) Account(hash common.Hash) (*types.SlimAccount, error) {
@@ -175,3 +183,18 @@ func (dl *diskLayer) Storage(accountHash, storageHash common.Hash) ([]byte, erro
 func (dl *diskLayer) Update(blockHash common.Hash, destructs map[common.Hash]struct{}, accounts map[common.Hash][]byte, storage map[common.Hash]map[common.Hash][]byte) *diffLayer {
 	return newDiffLayer(dl, blockHash, destructs, accounts, storage)
 }
+
+// stopGeneration aborts the state snapshot generation if it is currently running.
+func (dl *diskLayer) stopGeneration() {
+	dl.lock.RLock()
+	generating := dl.genMarker != nil
+	dl.lock.RUnlock()
+	if !generating {
+		return
+	}
+	if dl.genAbort != nil {
+		abort := make(chan *generatorStats)
+		dl.genAbort <- abort
+		<-abort
+	}
+}

core/state/snapshot/generate.go

@@ -631,16 +631,10 @@ func generateAccounts(ctx *generatorContext, dl *diskLayer, accMarker []byte) er
 		accMarker = nil
 		return nil
 	}
-	// Always reset the initial account range as 1 whenever recover from the
-	// interruption. TODO(rjl493456442) can we remove it?
-	var accountRange = accountCheckRange
-	if len(accMarker) > 0 {
-		accountRange = 1
-	}
 	origin := common.CopyBytes(accMarker)
 	for {
 		id := trie.StateTrieID(dl.root)
-		exhausted, last, err := dl.generateRange(ctx, id, rawdb.SnapshotAccountPrefix, snapAccount, origin, accountRange, onAccount, types.FullAccountRLP)
+		exhausted, last, err := dl.generateRange(ctx, id, rawdb.SnapshotAccountPrefix, snapAccount, origin, accountCheckRange, onAccount, types.FullAccountRLP)
 		if err != nil {
 			return err // The procedure it aborted, either by external signal or internal error.
 		}
@@ -652,7 +646,6 @@ func generateAccounts(ctx *generatorContext, dl *diskLayer, accMarker []byte) er
 			ctx.removeStorageLeft()
 			break
 		}
-		accountRange = accountCheckRange
 	}
 	return nil
 }

core/state/snapshot/snapshot.go

@@ -258,24 +258,11 @@ func (t *Tree) Disable() {
 	for _, layer := range t.layers {
 		switch layer := layer.(type) {
 		case *diskLayer:
-
-			layer.lock.RLock()
-			generating := layer.genMarker != nil
-			layer.lock.RUnlock()
-			if !generating {
-				// Generator is already aborted or finished
-				break
-			}
-			// If the base layer is generating, abort it
-			if layer.genAbort != nil {
-				abort := make(chan *generatorStats)
-				layer.genAbort <- abort
-				<-abort
-			}
-			// Layer should be inactive now, mark it as stale
-			layer.lock.Lock()
-			layer.stale = true
-			layer.lock.Unlock()
+			// TODO this function will hang if it's called twice. Will
+			// fix it in the following PRs.
+			layer.stopGeneration()
+			layer.markStale()
+			layer.Release()
 
 		case *diffLayer:
 			// If the layer is a simple diff, simply mark as stale
@@ -730,16 +717,11 @@ func (t *Tree) Rebuild(root common.Hash) {
 	for _, layer := range t.layers {
 		switch layer := layer.(type) {
 		case *diskLayer:
-			// If the base layer is generating, abort it and save
-			if layer.genAbort != nil {
-				abort := make(chan *generatorStats)
-				layer.genAbort <- abort
-				<-abort
-			}
-			// Layer should be inactive now, mark it as stale
-			layer.lock.Lock()
-			layer.stale = true
-			layer.lock.Unlock()
+			// TODO this function will hang if it's called twice. Will
+			// fix it in the following PRs.
+			layer.stopGeneration()
+			layer.markStale()
+			layer.Release()
 
 		case *diffLayer:
 			// If the layer is a simple diff, simply mark as stale