Github user maoling commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/584#discussion_r205941687
--- Diff: src/java/main/org/apache/zookeeper/server/DataTree.java ---
@@ -478,7 +478,10 @@ public void createNode(final String path, byte data[],
List<ACL> acl,
HashSet<String> list = ephemerals.get(ephemeralOwner);
if (list == null) {
list = new HashSet<String>();
- ephemerals.put(ephemeralOwner, list);
+ HashSet<String> _list;
+ if ((_list = ephemerals.putIfAbsent(ephemeralOwner,
list)) != null) {
+ list = _list;
+ }
}
synchronized (list) {
--- End diff --
Even if when `createNode` is called by multi-thread.this fix is also not
thread-safe.
Step1:One thread has acquired the `list` lock and enters into L487,add a
element into `list`
Step2:But at the same time just after Step1, another thread enters into
L483,the reference of `list` is pointed to the old `_list` object. It will
cause thread-unsafe
BTW: **Breaking Bad** is the best U.S.TV series
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