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https://issues.apache.org/jira/browse/LOG4J2-1457?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15371540#comment-15371540
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Leon Finker commented on LOG4J2-1457:
-------------------------------------
Loader.loadClass() could call Class.forName(className), which is equivalent to
Class.forName(className, true, currentLoader).
Or Loader.loadClass could call
getThreadContextClassLoader().loadClass(className), which ends up in
ClassLoader:
{noformat}
protected Class<?> loadClass(String name, boolean resolve)
throws ClassNotFoundException
{
synchronized (getClassLoadingLock(name)) {
{noformat}
That should also deadlock the same since it wants to acquire the class
loader+name lock.
> Class loader deadlock when using async logging
> ----------------------------------------------
>
> Key: LOG4J2-1457
> URL: https://issues.apache.org/jira/browse/LOG4J2-1457
> Project: Log4j 2
> Issue Type: Bug
> Affects Versions: 2.6.1
> Environment: On CentOS 6.7 and Java 1.8.0_60.
> Reporter: Leon Finker
> Priority: Critical
> Attachments: threaddump.txt
>
>
> We've encountered a class loading deadlock. Please review attached thread
> dump. Is it possible to have an option of pre-initializing the exception's
> thread stack on the caller's thread? It's hard to predict what libraries are
> doing in their classes' static initializers and may eventually end up logging
> and causing deadlock.
> In the attached thread dump here are the threads of interest:
> "Log4j2-AsyncLogger[AsyncContext@18b4aac2]1" #16 daemon prio=5 os_prio=0
> tid=0x00007ff870c7b000 nid=0x79f3 in Object.wait() [0x00007ff839142000]
> java.lang.Thread.State: RUNNABLE
> at java.lang.Class.forName0(Native Method)
> ...
> and
> "1A03340:Company:japan" #568 prio=5 os_prio=0 tid=0x00007ff871677000
> nid=0x725 runnable [0x00007ff74bd27000]
> ...<clinit>...
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