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Posted to commits@rocketmq.apache.org by "leeyiyu (via GitHub)" <gi...@apache.org> on 2023/06/09 07:05:01 UTC
[GitHub] [rocketmq] leeyiyu opened a new pull request, #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
leeyiyu opened a new pull request, #6883:
URL: https://github.com/apache/rocketmq/pull/6883
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### Which Issue(s) This PR Fixes
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Fixes #issue_id
### Brief Description
<!-- Write a brief description for your pull request to help the maintainer understand the reasons behind your changes. -->
### How Did You Test This Change?
```
@Test
public void computeIfAbsent() {
ConcurrentHashMap<String, String> map = new ConcurrentHashMap<>();
// map.computeIfAbsent("AaAa", key->map.computeIfAbsent("BBBB",key2->"42"));
ConcurrentHashMapUtils.computeIfAbsent(map, "AaAa", key -> map.computeIfAbsent("BBBB", key2 -> "42"));
}
```
<!-- In order to ensure the code quality of Apache RocketMQ, we expect every pull request to have undergone thorough testing. -->
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[GitHub] [rocketmq] ferrirW commented on pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "ferrirW (via GitHub)" <gi...@apache.org>.
ferrirW commented on PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#issuecomment-1591171105
> check this ,https://juejin.cn/post/7094561581631012878
>
> IMO, The original code has no problem.
It doesn't seem to be same bug. The blog mentions is https://bugs.openjdk.org/browse/JDK-8161372
I think @leeyiyu fixed is: https://bugs.openjdk.org/browse/JDK-8062841
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[GitHub] [rocketmq] ferrirW commented on a diff in pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "ferrirW (via GitHub)" <gi...@apache.org>.
ferrirW commented on code in PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#discussion_r1229589721
##########
common/src/main/java/org/apache/rocketmq/common/utils/ConcurrentHashMapUtils.java:
##########
@@ -40,10 +41,23 @@ public abstract class ConcurrentHashMapUtils {
* @see <a href="https://bugs.openjdk.java.net/browse/JDK-8161372">https://bugs.openjdk.java.net/browse/JDK-8161372</a>
*/
public static <K, V> V computeIfAbsent(ConcurrentMap<K, V> map, K key, Function<? super K, ? extends V> func) {
+ Objects.requireNonNull(func);
if (isJdk8) {
V v = map.get(key);
if (null == v) {
- v = map.computeIfAbsent(key, func);
+// v = map.computeIfAbsent(key, func);
Review Comment:
Comments can be removed
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[GitHub] [rocketmq] Codeprh commented on pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "Codeprh (via GitHub)" <gi...@apache.org>.
Codeprh commented on PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#issuecomment-1584314595
Reference dubbo link：https://github.com/apache/dubbo/pull/11987
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[GitHub] [rocketmq] xiaoyifang commented on pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "xiaoyifang (via GitHub)" <gi...@apache.org>.
xiaoyifang commented on PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#issuecomment-1584446339
> ConcurrentHashMapUtils.computeIfAbsent(map, "AaAa", key -> map.computeIfAbsent("BBBB", key2 -> "42"));
This has caused a deadlock. I think This should left for the user to avoid .
the above code is similar like
```
synchronized(obj){
synchronized(obj){
//logic
}
}
```
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[GitHub] [rocketmq] yuz10 merged pull request #6883: [ISSUE #6879] ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "yuz10 (via GitHub)" <gi...@apache.org>.
yuz10 merged PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883
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[GitHub] [rocketmq] leeyiyu commented on pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "leeyiyu (via GitHub)" <gi...@apache.org>.
leeyiyu commented on PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#issuecomment-1584298940
>
>
> check this ,https://juejin.cn/post/7094561581631012878
>
> IMO, The original code has no problem.
You can run this Case,CPU utilization will be 100%
```
@Test
public void computeIfAbsent() {
ConcurrentHashMap<String, String> map = new ConcurrentHashMap<>();
ConcurrentHashMapUtils.computeIfAbsent(map, "AaAa", key -> map.computeIfAbsent("BBBB", key2 -> "42"));
}
```
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[GitHub] [rocketmq] xiaoyifang commented on pull request #6883: ConcurrentHashMapUtils fails to solve the loop bug in JDK8
Posted by "xiaoyifang (via GitHub)" <gi...@apache.org>.
xiaoyifang commented on PR #6883:
URL: https://github.com/apache/rocketmq/pull/6883#issuecomment-1584276052
check this ,https://juejin.cn/post/7094561581631012878
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