(process) Process.waitFor does not release resources

Name: agR10195 Date: 11/26/2002



Alexey Gibadullin, ###@###.###

While working on the bug

    4637504 (process) REGRESSION: java.lang.Process does not clean up file
resources
    
I have extended Test.java from the bugreport to Test2.java

public class Test2 {
    public static void main(String argv[]) {
        int threads = Integer.parseInt(argv[0]);
        int processes = Integer.parseInt(argv[1]);
        
        for (int i = 0; i < threads; i++)
            (new MyThread(i, processes)).start();
    }
}

class MyThread extends Thread {
    private int number;
    private int processes;
    
    MyThread(int n, int p) {
        number = n;
        processes = p;
    }

    public void run() {
        for (int i = 0; i < processes; i++) {
            try {
                Runtime runtime = Runtime.getRuntime();
                Process process = runtime.exec("echo " + i);
                process.waitFor();
            } catch (Exception e) {
                System.out.println("Thread " + number + " got " + e);
                e.printStackTrace(System.out);
                return;
            }
            System.out.println("Thread " + number + ". Process " + i);
        }
    }
}

Test2 reveals that the bug #4637504 still present in Mantis-b07, if processes
are executed from a thread (4637504 was integrated into hopper).

% uname -a
SunOS novo152 5.8 Generic_108528-16 sun4u sparc SUNW,Ultra-5_10

% ../jdk1.4.2-b07/solaris-sparc/bin/java Test2 1 400
Thread 0. Process 0
Thread 0. Process 1
Thread 0. Process 2
...
Thread 0. Process 334
Thread 0. Process 335
Thread 0. Process 336
Thread 0. Process 337
Thread 0 got java.io.IOException: Too many open files
java.io.IOException: Too many open files
        at java.lang.UNIXProcess.forkAndExec(Native Method)
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:54)
        at java.lang.Runtime.execInternal(Native Method)
        at java.lang.Runtime.exec(Runtime.java:566)
        at java.lang.Runtime.exec(Runtime.java:428)
        at java.lang.Runtime.exec(Runtime.java:364)
        at java.lang.Runtime.exec(Runtime.java:326)
        at MyThread.run(Test2.java:24)
        
You may also increase number of threads. java.io.IOException is also thrown,
but it needs less number of processes:

% ../jdk1.4.2-b07/solaris-sparcv9/bin/java -d64 -server Test2 3 200
Thread 0. Process 0
Thread 1. Process 0
Thread 2. Process 0
Thread 0. Process 1
Thread 1. Process 1
Thread 2. Process 1
Thread 2. Process 2
Thread 0. Process 2
...
Thread 0. Process 108
Thread 1. Process 107
Thread 2. Process 110
Thread 0. Process 109
Thread 1. Process 108
Thread 2. Process 111
Thread 2. Process 112
Thread 0. Process 110
Thread 1. Process 109
Thread 2. Process 113
Thread 0. Process 111
Thread 1. Process 110
Thread 0 got java.io.IOException: Too many open files
java.io.IOException: Too many open files
        at java.lang.UNIXProcess.forkAndExec(Native Method)
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:54)
        at java.lang.Runtime.execInternal(Native Method)
        at java.lang.Runtime.exec(Runtime.java:566)
        at java.lang.Runtime.exec(Runtime.java:428)
        at java.lang.Runtime.exec(Runtime.java:364)
        at java.lang.Runtime.exec(Runtime.java:326)
        at MyThread.run(Test2.java:24)
Thread 1 got java.io.IOException: Too many open files
java.io.IOException: Too many open files
        at java.lang.UNIXProcess.forkAndExec(Native Method)
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:54)
        at java.lang.Runtime.execInternal(Native Method)
        at java.lang.Runtime.exec(Runtime.java:566)
        at java.lang.Runtime.exec(Runtime.java:428)
        at java.lang.Runtime.exec(Runtime.java:364)
        at java.lang.Runtime.exec(Runtime.java:326)
        at MyThread.run(Test2.java:24)
Thread 2. Process 114
Thread 2 got java.io.IOException: Too many open files
java.io.IOException: Too many open files
        at java.lang.UNIXProcess.forkAndExec(Native Method)
        at java.lang.UNIXProcess.<init>(UNIXProcess.java:54)
        at java.lang.Runtime.execInternal(Native Method)
        at java.lang.Runtime.exec(Runtime.java:566)
        at java.lang.Runtime.exec(Runtime.java:428)
        at java.lang.Runtime.exec(Runtime.java:364)
        at java.lang.Runtime.exec(Runtime.java:326)
        at MyThread.run(Test2.java:24)

The test fails on Solsparc and Solsparcv9 (5.8) and passes
on Windows2000, Linux Red Hat 7.2, Solx86 (5.8), Solsparc and Solsparcv9 (5.9).

======================================================================

Name: agR10195 Date: 11/26/2002



Alexey Gibadullin, ###@###.###

If I add

    process.destroy();
    
after

    process.waitFor();
    
the test passes fine even on Solsparc 5.8. However, the spec for
java.lang.Process says:

    public abstract int waitFor() throws InterruptedException
    
    causes the current thread to wait, if necessary, until the process
    represented by this Process object has terminated. This method returns
    immediately if the subprocess has already terminated. If the subprocess
    has not yet terminated, the calling thread will be blocked until the
    subprocess exits.
    
    
    public abstract void destroy()
    
    Kills the subprocess. The subprocess represented by this Process object
    is forcibly terminated.
    
Therefore, if the subprocess exits and waitFor() returns the exit value,
there is no need to call destroy(), since destroy() does nothing but killing
the subprocess.



======================================================================

Name: vrR10176 Date: 12/17/2002


JCK tests execution fails due to this bug. If JDK1.4.1 (b-21) or
JDK1.4.2 (b-10) is used to run JavaTest harness then a lot of JCK tests
fail in multiJVM mode with "java.io.IOException: Too many open files".

This bug can be observed in case of one thread.
To do this execute following test:
------------- test.java ----------------------
public class test {
    public static void main(String argv[]) {
        int i = 0;
        try {
            for(i = 0; i < 100000; i++) {
                Process p = Runtime.getRuntime().exec("ls");
            }
        } catch (java.io.IOException e) {
            System.out.println("Iteration: " + i + " Exception: " + e);
        }
    }
}
------------- log ----------------------------
$javac test.java
$
$java -version
java version "1.4.2-beta"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2-beta-b10)
Java HotSpot(TM) Client VM (build 1.4.2-beta-b10, mixed mode)
$
$uname -a
SunOS novo49 5.8 Generic_108528-15 sun4u sparc SUNW,Ultra-2
$
$java -Xfuture test
Iteration: 338 Exception: java.io.IOException: Too many open files
----------------------------------------------




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