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From "Henry Zongaro (JIRA)" <xalan-...@xml.apache.org>
Subject [jira] Commented: (XALANJ-2046) StringBufferPool + FastStringBuffer are not thread safe
Date Tue, 01 Feb 2005 19:57:17 GMT
     [ http://issues.apache.org/jira/browse/XALANJ-2046?page=comments#action_58435 ]
     
Henry Zongaro commented on XALANJ-2046:
---------------------------------------

Carlo, could I ask you to provide a link to any Eclipse bug report for this problem, so that
Xalan-J developers can check the status?

> StringBufferPool + FastStringBuffer are not thread safe
> -------------------------------------------------------
>
>          Key: XALANJ-2046
>          URL: http://issues.apache.org/jira/browse/XALANJ-2046
>      Project: XalanJ2
>         Type: Bug
>     Versions: 2.6
>  Environment: OS Name	Microsoft(R) Windows(R) Server 2003, Enterprise Edition	
> Version	5.2.3790  Build 3790	
> OS Manufacturer	Microsoft Corporation	
> System Type	X86-based PC	
> 4 processors
> Processor	x86 Family 15 Model 2 Stepping 9 GenuineIntel ~3056 Mhz	
> Processor	x86 Family 15 Model 2 Stepping 9 GenuineIntel ~3056 Mhz	
> Processor	x86 Family 15 Model 2 Stepping 9 GenuineIntel ~3056 Mhz	
> Processor	x86 Family 15 Model 2 Stepping 9 GenuineIntel ~3056 Mhz	
> J2EE Server Websphere version 5.2
> Java version = J2RE 1.4.1 IBM Windows 32 build cn1411-20031011b (JIT enabled: jitc),
Java Compiler = jitc, Java VM name = Classic VM
>     Reporter: Carlo Marchiori
>  Attachments: src.zip
>
> org.apache.xml.utils.StringBufferPool + org.apache.xml.utils.FastStringBuffer are not
thread safe.
> Under heavy load and after many invocation (I guess right after bytecode is compiled
into machine code) I get the following exception:
> Caused by: java.lang.NegativeArraySizeException
> 	at java.lang.StringBuffer.<init>(StringBuffer.java(Compiled Code))
> 	at org.apache.xml.utils.FastStringBuffer.toString(FastStringBuffer.java:433)
> 	at org.apache.xalan.templates.AVT.<init>(AVT.java(Compiled Code))
> 	at org.apache.xalan.processor.XSLTAttributeDef.processAVT_QNAME(XSLTAttributeDef.java(Compiled
Code))
> 	at org.apache.xalan.processor.XSLTAttributeDef.processValue(XSLTAttributeDef.java(Compiled
Code))
> 	at org.apache.xalan.processor.XSLTAttributeDef.setAttrValue(XSLTAttributeDef.java(Compiled
Code))
> 	at org.apache.xalan.processor.XSLTElementProcessor.setPropertiesFromAttributes(XSLTElementProcessor.java(Compiled
Code))
> 	at org.apache.xalan.processor.XSLTElementProcessor.setPropertiesFromAttributes(XSLTElementProcessor.java(Inlined
Compiled Code))
> 	at org.apache.xalan.processor.ProcessorTemplateElem.startElement(ProcessorTemplateElem.java(Compiled
Code))
> 	at org.apache.xalan.processor.StylesheetHandler.startElement(StylesheetHandler.java(Compiled
Code))
> 	at org.apache.xerces.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java(Compiled
Code))
> 	at org.apache.xerces.impl.XMLNamespaceBinder.handleStartElement(XMLNamespaceBinder.java(Compiled
Code))
> 	at org.apache.xerces.impl.XMLNamespaceBinder.startElement(XMLNamespaceBinder.java(Compiled
Code))
> 	at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidator.java(Compiled
Code))
> 	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java(Compiled
Code))
> 	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(XMLDocumentFragmentScannerImpl.java(Compiled
Code))
> 	at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java(Compiled
Code))
> 	at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.java:524)
> 	at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.java:580)
> 	at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:152)
> 	at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1169)
> 	at org.apache.xalan.processor.TransformerFactoryImpl.newTemplates(TransformerFactoryImpl.java:795)
> 	... 37 more
> I managed to see that the instance fields of the FastStringBuffer instance are  set to
random values (negative in particular), and so the exception occurs.
> I think that the problem is due to incorrect coding.
> In fact the code is equivalent to the following
> ----------------------------------------------------------
>    synchronized (...)
>    { 
>       //acquire an fsb instance from static pool
>    } 
>  
>    //write to fsb instance fields
>  
>    synchronized (...)
>    { 
>       //release the fsb instance into the static pool
>    } 
> ----------------------------------------------------------
>  
> When the first synchronized block ends the local thread cache is flushed
> to main memory. When the second synchronized block begins the local thread cache
> is refreshed from main memory, but in this way all intervening writes may be lost.
> I propose the StringBufferPool to have the lifetime of a transformation and to belong
to a single thread. I suggest further long running optimizations to be left to the underlying
plaftorm.
> Carlo.

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