DO NOT REPLY [Bug 41838] New: - HashMap infinite loop

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http://issues.apache.org/bugzilla/show_bug.cgi?id=41838

           Summary: HashMap infinite loop
           Product: Slide
           Version: 2.1
          Platform: Other
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Transaction Manager
        AssignedTo: [email protected]
        ReportedBy: [email protected]


When many concurrent threads try to connect to slide using the same user
account, an infinite loop may occur in HashMap.put or HashMap.transfer methods.

Stack trace of some threads inside JConsole :

Name: http-8095-Processor36
State: RUNNABLE
Total blocked: 142  Total waited: 14

Stack trace: 
java.util.HashMap.put(HashMap.java:385)
org.apache.slide.store.ExtendedStore.end(ExtendedStore.java:1029)
org.apache.slide.transaction.SlideTransaction.delistResource(SlideTransaction.java:377)
org.apache.slide.store.AbstractStore.delist(AbstractStore.java:1574)
org.apache.slide.store.AbstractStore.delist(AbstractStore.java:1559)
org.apache.slide.store.ExtendedStore.retrieveObject(ExtendedStore.java:581)
org.apache.slide.structure.StructureImpl.retrieve(StructureImpl.java:178)
org.apache.slide.structure.StructureImpl.retrieve(StructureImpl.java:160)
org.apache.slide.webdav.method.AbstractWebdavMethod.run(AbstractWebdavMethod.java:387)
org.apache.slide.webdav.WebdavServlet.service(WebdavServlet.java:155)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
…

Name: http-8095-Processor46
State: RUNNABLE
Total blocked: 44  Total waited: 12

Stack trace: 
java.util.HashMap.transfer(HashMap.java:476)
java.util.HashMap.resize(HashMap.java:455)
java.util.HashMap.addEntry(HashMap.java:745)
java.util.HashMap.put(HashMap.java:395)
org.apache.slide.store.ExtendedStore.end(ExtendedStore.java:1029)


The ExtendedStore.java, line 1029 :

suspendedLocks.put(txId, locks.get());

Many threads use the same ExtendedStore instance, so the same suspendedLocks
instance.

suspendedLocks is not a synchronized Map.

The following link
http://blogs.opensymphony.com/plightbo/2005/07/hashmapget_can_cause_an_infini.html
explains clearly the behaviour of "non synchronized Map updated by concurrent
threads".

The patch is  :

private Map suspendedLocks = Collections.synchronizedMap(new HashMap());

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