debugging startup issue in jenkins.diagnosis.HsErrPidList

[PJ Fanning]

I have an issue when starting Jenkins. The Jenkins instance has been in use for a few months but after installing a recent Jenkins, the instance hangs on restart. This hang only happens with the --daemon startup option and oddly, does not occur if I use the same params but omit the --daemon param.

This works but the equivalent --daemon startup fails:
usr/bin/java -Xmx10g -Xms5g -DJENKINS_HOME=/data/jenkins -jar /usr/lib/jenkins/jenkins.war --logfile=/var/log/jenkins/jenkins.log --webroot=/var/cache/jenkins/war --httpPort=9000 --ajp13Port=-1 --debug=9 --handlerCountMax=100 --handlerCountMaxIdle=20 --prefix=/jenkins-cl

The hang occurs here (this locks out all other extensions):
  "UpdateCenter.init" #101 daemon prio=5 os_prio=0 tid=0x00007f71f8001800 nid=0x2f6a runnable [0x00007f747aeeb000]
   java.lang.Thread.State: RUNNABLE
        at java.io.UnixFileSystem.list(Native Method)
        at java.io.File.list(File.java:1122)
        at org.apache.tools.ant.DirectoryScanner.scandir(DirectoryScanner.java:1257)
        at org.apache.tools.ant.DirectoryScanner.scandir(DirectoryScanner.java:1211)
        at org.apache.tools.ant.DirectoryScanner.scandir(DirectoryScanner.java:1173)
        at org.apache.tools.ant.DirectoryScanner.checkIncludePatterns(DirectoryScanner.java:955)
        at org.apache.tools.ant.DirectoryScanner.scan(DirectoryScanner.java:909)
        - locked <0x00000005956fc980> (a org.apache.tools.ant.DirectoryScanner)
        at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:499)
        at jenkins.diagnosis.HsErrPidList.scan(HsErrPidList.java:113)
        at jenkins.diagnosis.HsErrPidList.<init>(HsErrPidList.java:56)
        at jenkins.diagnosis.HsErrPidList$$FastClassByGuice$$b61c3f44.newInstance(<generated>)
        at com.google.inject.internal.cglib.reflect.$FastConstructor.newInstance(FastConstructor.java:40)

I've tried enabling fine debug logging (--debug=9) and tried other strategies based on https://wiki.jenkins-ci.org/display/JENKINS/Logging but so far, I can't get the fine logs to appear in my log file (--logfile option above).

Would anyone have any advice on how to get fine logs from jenkins.diagnosis.HsErrPidList? Or is there a way to disable this diagnostic? I suspect that there is a file permissions issue or something like that.

Any help would be appreciated.