rpc, whisper, xeth: fix RPC message retrieval data race

xeth/whisper_filter.go

@@ -1,26 +1,84 @@
 // Contains the external API side message filter for watching, pooling and polling
-// matched whisper messages.
+// matched whisper messages, also serializing data access to avoid duplications.
 
 package xeth
 
-import "time"
+import (
+	"sync"
+	"time"
+
+	"github.com/ethereum/go-ethereum/common"
+)
 
 // whisperFilter is the message cache matching a specific filter, accumulating
 // inbound messages until the are requested by the client.
 type whisperFilter struct {
-	id      int              // Filter identifier
-	cache   []WhisperMessage // Cache of messages not yet polled
-	timeout time.Time        // Time when the last message batch was queries
+	id  int      // Filter identifier for old message retrieval
+	ref *Whisper // Whisper reference for old message retrieval
+
+	cache  []WhisperMessage         // Cache of messages not yet polled
+	skip   map[common.Hash]struct{} // List of retrieved messages to avoid duplication
+	update time.Time                // Time of the last message query
+
+	lock sync.RWMutex // Lock protecting the filter internals
+}
+
+// newWhisperFilter creates a new serialized, poll based whisper topic filter.
+func newWhisperFilter(id int, ref *Whisper) *whisperFilter {
+	return &whisperFilter{
+		id:  id,
+		ref: ref,
+
+		update: time.Now(),
+		skip:   make(map[common.Hash]struct{}),
+	}
+}
+
+// messages retrieves all the cached messages from the entire pool matching the
+// filter, resetting the filter's change buffer.
+func (w *whisperFilter) messages() []WhisperMessage {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	w.cache = nil
+	w.update = time.Now()
+
+	w.skip = make(map[common.Hash]struct{})
+	messages := w.ref.Messages(w.id)
+	for _, message := range messages {
+		w.skip[message.ref.Hash] = struct{}{}
+	}
+	return messages
 }
 
 // insert injects a new batch of messages into the filter cache.
-func (w *whisperFilter) insert(msgs ...WhisperMessage) {
-	w.cache = append(w.cache, msgs...)
+func (w *whisperFilter) insert(messages ...WhisperMessage) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	for _, message := range messages {
+		if _, ok := w.skip[message.ref.Hash]; !ok {
+			w.cache = append(w.cache, messages...)
+		}
+	}
 }
 
 // retrieve fetches all the cached messages from the filter.
 func (w *whisperFilter) retrieve() (messages []WhisperMessage) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
 	messages, w.cache = w.cache, nil
-	w.timeout = time.Now()
+	w.update = time.Now()
+
 	return
 }
+
+// activity returns the last time instance when client requests were executed on
+// the filter.
+func (w *whisperFilter) activity() time.Time {
+	w.lock.RLock()
+	defer w.lock.RUnlock()
+
+	return w.update
+}