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Date: Sun, 20 Mar 2011 19:50:06 +0000 (UTC)
From: "Phil Steitz (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
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 <842551904.8056.1299682379438.JavaMail.tomcat@hel.zones.apache.org>
Subject: [jira] [Updated] (POOL-184) Premature starvation in
 GenericObjectPool when borrowObject() and evict() are executed concurrently
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     [ https://issues.apache.org/jira/browse/POOL-184?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Phil Steitz updated POOL-184:
-----------------------------

    Fix Version/s: 1.5.6

> Premature starvation in GenericObjectPool when borrowObject() and evict() are executed concurrently
> ---------------------------------------------------------------------------------------------------
>
>                 Key: POOL-184
>                 URL: https://issues.apache.org/jira/browse/POOL-184
>             Project: Commons Pool
>          Issue Type: Bug
>    Affects Versions: 1.5.5
>         Environment: java 1.6.0_24
> Ubuntu 10.10
>            Reporter: Adrian Nistor
>             Fix For: 1.5.6
>
>         Attachments: Test01.java, stall.txt
>
>
> Hi,
> I am encountering a deadlock in GenericObjectPool. It appears in version 1.5.5 
> and also in revision 1079385 (March 8th 2011).
> The deadlock manifests when calling borrowObject() and evict() in parallel. I 
> have inlined a test that exposes this problem. For this test, the expected 
> output is:
> Expected output:
> 0
> 1
> 2
> 3
> 4
> .....
> 498
> 499
> DONE
> But when the bug manifests (almost always for this test), the output is:
> Bug output:
> 0
> 1
> 2
> 3
> 4
> When the bug manifests, the test does not finish, it just gets stuck after
> printing several values (in this run: 0 1 2 3 4, but in other runs may be
> 0 1 2 .. 18 or 0 1 2 or some other value).
> When the loop limit is small (e.g., 11 instead of 5000), the test does finish.
> Also, when running sequentially:
>  
>     Pool.borrowObject();
>     Pool.evict();
> or vice-versa
>     Pool.evict();
>     Pool.borrowObject();
> the test still finishes. 
> Is this a bug? Is there a patch for it?
> Thanks!
> Adrian
> ================================================================================
> This test is for version 1.5.5. For revision 1079385 one should replace 
> setMaxActive() with setMaxTotal()
> ================================================================================
> package org.apache.commons.pool.impl;
> import org.apache.commons.pool.PoolableObjectFactory;
> public class Test01 
> {
>     public static void main(String[] args) throws Exception 
>     {
>         Test01 test = new Test01();
>         test.test();
>     }
>     
>     SimpleFactory Factory = null;
>     GenericObjectPool Pool = null;
>     Object Obj = null;
>     public void test() throws Exception 
>     {
>         Factory = new SimpleFactory();
>         Pool = new GenericObjectPool(Factory);
>         Pool.setMaxActive(1);
>         Pool.addObject();
>         
>         for(int i=0; i<5000; i++)
>         {
>             Thread one = new MyThread(1);
>             Thread two = new MyThread(2);
>             one.start();
>             two.start();
>             one.join();
>             two.join();
>             
>             Pool.returnObject(Obj);
>             if(i%10==0)
>             {
>                 System.out.println(i/10);
>             }
>         }
>         System.out.println("DONE");
>     }
>     private class MyThread extends Thread 
>     {
>         int _tid;
>         public MyThread(int tid) 
>         {
>             _tid = tid;
>         }
>         public void run() 
>         {
>             try 
>             {
>                 if(_tid == 1) 
>                 {
>                     Obj = Pool.borrowObject();
>                 }
>                 if (_tid == 2) 
>                 {
>                     try
>                     {
>                         Pool.evict();
>                     } catch (Exception e) {}
>                 }
>             } 
>             catch(Exception e) 
>             {
>                 throw new RuntimeException(e);
>             }
>         }
>     }
>     private class SimpleFactory implements PoolableObjectFactory
>     {
>         public SimpleFactory() {}
>         public Object makeObject() { return new String("testing"); }
>         public void destroyObject(Object obj) {}
>         public boolean validateObject(Object obj) {return true;}
>         public void activateObject(Object obj) throws Exception {}
>         public void passivateObject(Object obj) throws Exception {}
>         public boolean isThrowExceptionOnActivate() {return true;}
>     }
> }
> ================================================================================

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