kern/107109: [nfs] Netbeans/Eclipse/Java provoke deadlocks when used with NFS

[Joerg Lehners]

The following reply was made to PR kern/107109; it has been noted by GNATS.

From: "Joerg Lehners" <Joerg.Lehners at Informatik.Uni-Oldenburg.DE>
To: bug-followup at FreeBSD.org
Cc:  
Subject: kern/107109: [nfs] Netbeans/Eclipse/Java provoke deadlocks when used
 with NFS
Date: Thu, 25 Jan 2007 13:57:40 +0100 (MET)

 I have experimented further and narrowed down the problem somewhat.
 In the meantime I upgraded to FreeBSD 6.2-STABLE as of 8. Jan 2007
 and Java 1.5.0 p4 (patchkit 4 from a few days ago).
 
 I got someone to wrote a short Java program for me (thanks to Felix
 Kronlage!) that is able to provoke the problem more easily than with
 Netbeans and 'do this and than that and ...'.
 
 With the program running the Java process locks up after a few seconds
 of running it, sometime it takes longer. As I suspected initially it is the
 intermixed fork()ing and stat()ing of NFS files/directories in different
 threads and some other magic.
 I tried the Java program with Java 1.5.0 for FreeBSD (patchkit 4), which
 locks up after some seconds. With Java 1.5.0 for Linux the program crashes
 after some seconds with some HotSpot error (which is not uncommon for
 Java 1.5.0 for Linux on FreeBSD 6). With Java 1.6.0 for Linux the
 program ran for many minutes without any crashes or lockups jet.
 I also tried Java 1.4.2 for FreeBSD (built from Java SCSL source code with
 patchkit 8): no crashes or lockups even after many minutes of running.
 
 So there seems to be some magic in Java 1.5.0 for FreeBSD (built from
 Java SCSL source code with at least patchkit p3 and p4) that provoke
 some deadlock in the kernel when threads do execute fork() and stat()
 on NFS files/directories intermixed.
 
 In the program NFSStressTest.java the variable 'directories' must list
 some directories that are accessible via NFS.
 
 --- NFSStressTest.java begins here ---
 
 import java.io.*;
 
 public class NFSStressTest {
 
  	public static void main(String[] args) {
 
  		int intervall= 1000;
  		boolean debug= true;
 
  		String[] directories = { "/user/admin/joerg/Src/%Archiv",
  						"/user/admin/joerg/Src/%DONE",
  						"/user/admin/joerg/Bin" };
 
  		String[] commands = { "/bin/echo 'hallo'",
  					"/bin/ls /tmp" ,
  					"/sbin/md5 /bin/ls" };
 
  		IOMaker[] ioMakers= new IOMaker[directories.length];
  		CMDMaker[] cmdMakers= new CMDMaker[commands.length];
 
  		for(int i=0;i<directories.length;i++) {
  			ioMakers[i]= new IOMaker(directories[i], intervall);
  			ioMakers[i].setDebug(false);
  			ioMakers[i].start();
  		}
 
  		for(int i=0;i<commands.length;i++) {
  			cmdMakers[i]= new CMDMaker(commands[i], intervall);
  			cmdMakers[i].setDebug(true);
  			cmdMakers[i].start();
  		}
 
  	}
 }
 
 
 
 class IOMaker extends Thread {
 
  	private String directory;
  	private int intervall;
  	private boolean debug= false;
 
  	IOMaker(String directory) {
  		this.directory= directory;
  	}
 
  	IOMaker(String directory, int intervall) {
  		this.directory= directory;
  		this.intervall= intervall;
  	}
 
  	void setDebug(boolean debug) {
  		this.debug= debug;
  	}
 
  	public void run() {
 
  		File myDirectory= new File(this.directory);
 
  		while(true) {
  			File[] myFiles= myDirectory.listFiles();
 
  			if(myFiles == null)
  				break;
 
  			for(int i=0;i<myFiles.length;i++) {
 
  				String absolutePath= myFiles[i].getAbsolutePath();
  				long lastModified= myFiles[i].lastModified();
 
  				if(this.debug) {
  					System.out.println(this +": " + absolutePath +" : " + lastModified);
  				}
  			}
 
  			Thread.yield();
  			try {
  				Thread.sleep(this.intervall);
  			} catch (Exception e) {
  				System.out.println("Caught exception: " + e.getMessage());
  				e.printStackTrace();
  			}
  		}
  	}
 }
 
 class CMDMaker extends Thread {
 
  	private String command;
  	private int intervall;
  	private boolean debug= false;
 
  	CMDMaker(String command, int intervall) {
  		this.command= command;
  		this.intervall= intervall;
  	}
 
  	void setDebug(boolean debug) {
  		this.debug= debug;
  	}
 
  	public void run() {
 
  		while(true) {
  			try {
  				if(this.debug) {
  					System.out.println("command: " + this.command);
  				}
  				Runtime.getRuntime().exec(this.command);
  			} catch (IOException e) {
  				System.out.println("Caught exception in CMDMaker ("+ this.command +
  						           ": "+ e.getMessage());
  				e.printStackTrace();
  			}
 
  			Thread.yield();
  			try {
  				Thread.sleep(this.intervall);
  			} catch (Exception e) {
  				System.out.println("Caught exception: " + e.getMessage());
  				e.printStackTrace();
  			}
  		}
  	}
 }
 
 --- NFSStressTest.java ends here ---
 
 -- 
 Mail: Joerg.Lehners at Informatik.Uni-Oldenburg.DE    Tel: 2198
 Real: Joerg Lehners, Informatik ARBI, Uni Oldenburg, D-26111 Oldenburg
 Unwoerter: Kostensenkung - Gewinnmaximierung - billig, billig, billig