From 793cb095b03ef70e05d87e76932829ba1524556e Mon Sep 17 00:00:00 2001
From: Xiang Li <xiang.li@coreos.com>
Date: Fri, 5 Dec 2014 11:55:01 -0800
Subject: [PATCH] store: fix race in watcher_hub

Get the lock before modifing the global objects in the hub.
---
 store/watcher_hub.go | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/store/watcher_hub.go b/store/watcher_hub.go
index 0284e66bd..89926563f 100644
--- a/store/watcher_hub.go
+++ b/store/watcher_hub.go
@@ -33,7 +33,7 @@ import (
 // event happens between the end of the first watch command and the start
 // of the second command.
 type watcherHub struct {
-	mutex        sync.Mutex // protect the hash map
+	mutex        sync.Mutex
 	watchers     map[string]*list.List
 	count        int64 // current number of watchers.
 	EventHistory *EventHistory
@@ -71,6 +71,8 @@ func (wh *watcherHub) watch(key string, recursive, stream bool, index, storeInde
 		hub:        wh,
 	}
 
+	wh.mutex.Lock()
+	defer wh.mutex.Unlock()
 	// If the event exists in the known history, append the EtcdIndex and return immediately
 	if event != nil {
 		event.EtcdIndex = storeIndex
@@ -78,9 +80,6 @@ func (wh *watcherHub) watch(key string, recursive, stream bool, index, storeInde
 		return w, nil
 	}
 
-	wh.mutex.Lock()
-	defer wh.mutex.Unlock()
-
 	l, ok := wh.watchers[key]
 
 	var elem *list.Element