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  1. JDK
  2. JDK-8146271

File system contention in debug print via XPathFactory.newInstance

    Details

    • Subcomponent:
    • Resolved In Build:
      b150
    • CPU:
      x86_64
    • OS:
      windows_7

      Description

      FULL PRODUCT VERSION :
      java version "1.7.0_51"
      Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
      Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

      ADDITIONAL OS VERSION INFORMATION :
      Specifically encountered on Windows 6.1.6701, but affects all OSes

      A DESCRIPTION OF THE PROBLEM :
      I ran XPathFactory.newInstance(String, String, ClassLoader) and noticed heavy locking on the filesystem due to classloader activity. The problem appears to be in XPathFactoryFinder (line 293 in jdk8u20 / line 312 in jdk7u51):

              debugPrintln("loaded " + className + " from " + which(clazz));

      The seemingly innocuous call, which(clazz), occurs even though debugging is disabled and results in unnecessary I/O and contention. A simple solution would be to wrap the call to debugPrintln in an if (debug) block. Here is a stack trace of the problem in jdk7u51, which will be very similar in jdk8u20:

         java.lang.Thread.State: BLOCKED (on object monitor)
      at java.util.zip.ZipFile.getEntry(ZipFile.java:304)
      - waiting to lock <0x0000000780e67928> (a java.util.jar.JarFile)
      at java.util.jar.JarFile.getEntry(JarFile.java:226)
      at java.util.jar.JarFile.getJarEntry(JarFile.java:209)
      at sun.misc.URLClassPath$JarLoader.getResource(URLClassPath.java:840)
      at sun.misc.URLClassPath$JarLoader.findResource(URLClassPath.java:818)
      at sun.misc.URLClassPath.findResource(URLClassPath.java:176)
      at java.net.URLClassLoader$2.run(URLClassLoader.java:551)
      at java.net.URLClassLoader$2.run(URLClassLoader.java:549)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.net.URLClassLoader.findResource(URLClassLoader.java:548)
      at java.lang.ClassLoader.getResource(ClassLoader.java:1147)
      at javax.xml.xpath.SecuritySupport$5.run(SecuritySupport.java:106)
      at java.security.AccessController.doPrivileged(Native Method)
      at javax.xml.xpath.SecuritySupport.getResourceAsURL(SecuritySupport.java:99)
      at javax.xml.xpath.XPathFactoryFinder.which(XPathFactoryFinder.java:549)
      at javax.xml.xpath.XPathFactoryFinder.which(XPathFactoryFinder.java:531)
      at javax.xml.xpath.XPathFactoryFinder.createInstance(XPathFactoryFinder.java:296)
      at javax.xml.xpath.XPathFactoryFinder.createInstance(XPathFactoryFinder.java:283)
      at javax.xml.xpath.XPathFactory.newInstance(XPathFactory.java:260)


      ADDITIONAL REGRESSION INFORMATION:
      java version "1.7.0_51"
      Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
      Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

      STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
      Start multiple threads that repeatedly do this:

      XPath xpath = XPathFactory.newInstance(XPathFactory.DEFAULT_OBJECT_MODEL_URI, "org.apache.xpath.jaxp.XPathFactoryImpl", null).newXPath();

      EXPECTED VERSUS ACTUAL BEHAVIOR :
      EXPECTED -
      No I/O or blocking between threads calling XPathFactory.newInstance with debug disabled.
      ACTUAL -
      I/O and blocking between threads calling XPathFactory.newInstance with debug disabled.

      REPRODUCIBILITY :
      This bug can be reproduced always.

      ---------- BEGIN SOURCE ----------
      XPath xpath = XPathFactory.newInstance(XPathFactory.DEFAULT_OBJECT_MODEL_URI, "org.apache.xpath.jaxp.XPathFactoryImpl", null).newXPath();
      ---------- END SOURCE ----------

      CUSTOMER SUBMITTED WORKAROUND :
      XPath xpath = new org.apache.xpath.jaxp.XPathFactoryImpl().newXPath();

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            • Assignee:
              aefimov Aleksej Efimov
              Reporter:
              webbuggrp Webbug Group
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              Dates

              • Created:
                Updated:
                Resolved: