[
https://issues.apache.org/jira/browse/KYLIN-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16631400#comment-16631400
]
XiaoXiang Yu edited comment on KYLIN-3578 at 9/28/18 6:16 AM:
--------------------------------------------------------------
{quote}private final ReentrantLock lock = new ReentrantLock();{quote}
{quote}{{if (delta < 0) {}}
{{ synchronized (lock) {}}
{{ lock.notifyAll();}}
{{ }}}
{{}}}
{quote}
This code above seems violates good practice, the reporter says use intrinsic
lock on high-level lock is a mistake, use tryLock method of high-level lock is
correct.
But code above just regard _+lock+_ object as a normal object and use tryLock
to replace it a real mistake. In my view, it looks like a trick other than a
mistake.
So it is no need to repair it. It has no relation with intrinsic lock on
high-level lock mistake.
[oracle locksync
doc|https://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html]
[Chinese
Javadoc|https://github.com/hit-lacus/kylin/blob/86108c41552dea1f248abb71ddbeac8f82900005/core-common/src/main/java/org/apache/kylin/common/util/MemoryBudgetController.java]
[Do not synchronize on the intrinsic locks of high-level concurrency
objects|https://wiki.sei.cmu.edu/confluence/display/java/LCK03-J.+Do+not+synchronize+on+the+intrinsic+locks+of+high-level+concurrency+objects]
was (Author: hit_lacus):
{quote}if (delta < 0) {
synchronized (lock) {
lock.notifyAll();
}
}{quote}
This code above seems violates good practice, but it's just regard _+lock+_
object as a normal object. It looks like a trick other than a mistake.
So it is no need to repair it. It has no relation with intrinsic lock on
high-level lock.
[oracle locksync
doc|https://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html]
[Chinese
Javadoc|https://github.com/hit-lacus/kylin/blob/86108c41552dea1f248abb71ddbeac8f82900005/core-common/src/main/java/org/apache/kylin/common/util/MemoryBudgetController.java]
[Do not synchronize on the intrinsic locks of high-level concurrency
objects|https://wiki.sei.cmu.edu/confluence/display/java/LCK03-J.+Do+not+synchronize+on+the+intrinsic+locks+of+high-level+concurrency+objects]
> Do not synchronize on the intrinsic locks of high-level concurrency objects
> ---------------------------------------------------------------------------
>
> Key: KYLIN-3578
> URL: https://issues.apache.org/jira/browse/KYLIN-3578
> Project: Kylin
> Issue Type: Bug
> Reporter: Ted Yu
> Assignee: XiaoXiang Yu
> Priority: Major
> Fix For: v2.6.0
>
>
> From
> core-common/src/main/java/org/apache/kylin/common/util/MemoryBudgetController.java
> :
> {code}
> private final ReentrantLock lock = new ReentrantLock();
> ...
> synchronized (lock) {
> {code}
> See the following for why such practice is to be avoided:
> https://wiki.sei.cmu.edu/confluence/display/java/LCK03-J.+Do+not+synchronize+on+the+intrinsic+locks+of+high-level+concurrency+objects
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