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Date: Mon, 29 Jan 2007 05:25:49 -0800 (PST)
From: "Elena Semukhina (JIRA)" <jira@apache.org>
To: commits@harmony.apache.org
Subject: [jira] Updated: (HARMONY-2982) [drlvm][smoke tests] Smoke test
 classloader.StressLoader fails intermittently
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     [ https://issues.apache.org/jira/browse/HARMONY-2982?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Elena Semukhina updated HARMONY-2982:
-------------------------------------

    Attachment: H-2982.patch

It seems that java.net.URLClassLoader implementation is not thread safe. It should take care of synchronization on modification of resCache, which is an IdentityHashMap object.

The spec of java.util.IdentityHashMap reads: "Note that this implementation is not synchronized. If multiple threads access this map concurrently, and at least one of the threads modifies the map structurally, it must be synchronized externally."

The patch provides synchronization on get/put methods.

I also added missed synchronization on the HashMap "extentions" field in the addURL(...) method although it seems that both addURL() methods are not used at all.

I ran the classloader.StressLoader test iteratively hundreds of times with the patch and didn't see the failures described in the report.
 

> [drlvm][smoke tests] Smoke test classloader.StressLoader fails intermittently
> -----------------------------------------------------------------------------
>
>                 Key: HARMONY-2982
>                 URL: https://issues.apache.org/jira/browse/HARMONY-2982
>             Project: Harmony
>          Issue Type: Bug
>          Components: DRLVM
>            Reporter: Elena Semukhina
>         Attachments: H-2982.patch
>
>
> I observe two sorts of intermittent failures. They occur in JIT mode. I saw them on linux ia32 build: 
> 1. java.lang.NullPointerException
> 	at java.net.URLClassLoader.explore(URLClassLoader.java:1200)
> 	at java.net.URLClassLoader.findResourceImpl(URLClassLoader.java:809)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java:667)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java)
> 	at java.security.AccessController.doPrivilegedImpl(Unknown Source)
> 	at java.security.AccessController.doPrivileged(Unknown Source)
> 	at java.net.URLClassLoader.findResource(URLClassLoader.java:665)
> 	at java.lang.ClassLoader$BootstrapLoader.findResource(Unknown Source)
> 	at java.lang.ClassLoader.getResource(Unknown Source)
> 	at java.lang.ClassLoader.getResourceAsStream(Unknown Source)
> 	at java.lang.ClassLoader.getSystemResourceAsStream(Unknown Source)
> 	at classloader.LogLoader.loadClass(Unknown Source)
> 	at classloader.StressLoader.run(Unknown Source)
> 2. java.lang.ArrayIndexOutOfBoundsException
> 	at java.util.IdentityHashMap.rehash(IdentityHashMap.java:501)
> 	at java.util.IdentityHashMap.put(IdentityHashMap.java:463)
> 	at java.net.URLClassLoader.findResourceImpl(URLClassLoader.java:720)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java:667)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java)
> 	at java.security.AccessController.doPrivilegedImpl(Unknown Source)
> 	at java.security.AccessController.doPrivileged(Unknown Source)
> 	at java.net.URLClassLoader.findResource(URLClassLoader.java:665)
> 	at java.lang.ClassLoader$BootstrapLoader.findResource(Unknown Source)
> 	at java.lang.ClassLoader.getResource(Unknown Source)
> 	at java.lang.ClassLoader.getResourceAsStream(Unknown Source)
> 	at java.lang.ClassLoader.getSystemResourceAsStream(Unknown Source)
> 	at classloader.LogLoader.loadClass(Unknown Source)
> 	at classloader.StressLoader.run(Unknown Source)
> java.lang.ArrayIndexOutOfBoundsException
> 	at java.util.IdentityHashMap.rehash(IdentityHashMap.java:501)
> 	at java.util.IdentityHashMap.put(IdentityHashMap.java:463)
> 	at java.net.URLClassLoader.findResourceImpl(URLClassLoader.java:720)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java:667)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java)
> 	at java.security.AccessController.doPrivilegedImpl(Unknown Source)
> 	at java.security.AccessController.doPrivileged(Unknown Source)
> 	at java.net.URLClassLoader.findResource(URLClassLoader.java:665)
> 	at java.lang.ClassLoader$BootstrapLoader.findResource(Unknown Source)
> 	at java.lang.ClassLoader.getResource(Unknown Source)
> 	at java.lang.ClassLoader.getResourceAsStream(Unknown Source)
> 	at java.lang.ClassLoader.getSystemResourceAsStream(Unknown Source)
> 	at classloader.LogLoader.loadClass(Unknown Source)
> 	at classloader.StressLoader.run(Unknown Source)
> java.lang.ArrayIndexOutOfBoundsException
> 	at java.util.IdentityHashMap.rehash(IdentityHashMap.java:501)
> 	at java.util.IdentityHashMap.put(IdentityHashMap.java:463)
> 	at java.net.URLClassLoader.findResourceImpl(URLClassLoader.java:720)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java:667)
> 	at java.net.URLClassLoader$5.run(URLClassLoader.java)
> 	at java.security.AccessController.doPrivilegedImpl(Unknown Source)
> 	at java.security.AccessController.doPrivileged(Unknown Source)
> 	at java.net.URLClassLoader.findResource(URLClassLoader.java:665)
> 	at java.lang.ClassLoader$BootstrapLoader.findResource(Unknown Source)
> 	at java.lang.ClassLoader.getResource(Unknown Source)
> 	at java.lang.ClassLoader.getResourceAsStream(Unknown Source)
> 	at java.lang.ClassLoader.getSystemResourceAsStream(Unknown Source)
> 	at classloader.LogLoader.loadClass(Unknown Source)
> 	at classloader.StressLoader.run(Unknown Source)

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