From 0f7cef0cf7a4fa40d3ad68ad908181a06205b077 Mon Sep 17 00:00:00 2001
From: Zhangmei Li <lizhangmei@baidu.com>
Date: Mon, 21 Mar 2022 18:04:23 +0800
Subject: [PATCH] fix prev may change after empty judgment

Change-Id: I6814e588c67018b13fcefbc373f02912dbf08c6a
---
 .../java/com/baidu/hugegraph/backend/cache/RamCache.java   | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/RamCache.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/RamCache.java
index be2b44b089..0bfda706db 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/RamCache.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/backend/cache/RamCache.java
@@ -395,6 +395,7 @@ public LinkNode<K, V> enqueue(LinkNode<K, V> node) {
 
             while (true) {
                 LinkNode<K, V> last = this.rear.prev;
+                assert last != this.empty : last;
 
                 // TODO: should we lock the new `node`?
                 List<Lock> locks = this.lock(last, this.rear);
@@ -446,7 +447,7 @@ public LinkNode<K, V> dequeue() {
                     }
 
                     // Break the link between the `head` and `first`
-                    assert first.next != null;
+                    assert first.next != null && first.next != this.empty;
                     this.head.next = first.next;
                     first.next.prev = this.head;
 
@@ -469,12 +470,12 @@ public LinkNode<K, V> remove(LinkNode<K, V> node) {
             assert node != this.head && node != this.rear;
 
             while (true) {
-                if (node.prev == this.empty || node.next == this.empty) {
+                LinkNode<K, V> prev = node.prev;
+                if (prev == this.empty || node.next == this.empty) {
                     // Ignore the `node` if it has been removed
                     return null;
                 }
 
-                LinkNode<K, V> prev = node.prev;
                 List<Lock> locks = this.lock(prev, node);
                 try {
                     if (prev != node.prev) {