Name: jl125535 Date: 11/14/2003


FULL PRODUCT VERSION :
java version "1.4.2_02"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_02-b03)
Java HotSpot(TM) Client VM (build 1.4.2_02-b03, mixed mode)


FULL OS VERSION :
Linux rhel.versedge.com 2.4.21-4.EL #1 Fri Oct 3 18:13:58 EDT 2003 i686 i686 i386 GNU/Linux
This is RHEL 3.0

EXTRA RELEVANT SYSTEM CONFIGURATION :
gcc version 3.2.3 20030502 (Red Hat Linux 3.2.3-20)


A DESCRIPTION OF THE PROBLEM :
When using JNI calls in multi-threaded program, the native call ("system()") sometimes return with error of "No child processes".

When setting LD_ASSUME_KERNEL=2.4, the problem disapear.


STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Below is a small program to reproduce it. In general, the program creates two threads which invoking "system" system call 10 times each in parallel.

Create the two files below and run the following commands:
> /usr/java/j2sdk1.4.2_02/bin/javac LinuxBug.java
> cc -I /usr/java/j2sdk1.4.2_02/include -I /usr/java/j2sdk1.4.2_02/include/linux LinuxBug.c -shared -o libLinuxBug.so
> /usr/java/j2sdk1.4.2_02/bin/java -Djava.library.path=`pwd` LinuxBug





ERROR MESSAGES/STACK TRACES THAT OCCUR :
"No child processes" (from strerror)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
LinuxBug.java
-------------
public class LinuxBug extends Thread {
        public LinuxBug (String cmd) {
                m_cmd = cmd;
        }

        public void run () {
                for (int j=0; j<10; j++) {
                    int i = systemCall (m_cmd);
                    System.out.println ("systemCall " + m_cmd + " ("
                                        +j+") return " + i);
                }
        }

        private String m_cmd = null;

    native static int systemCall (String arg);
    public static void main (String argv[])
   {
        System.loadLibrary("LinuxBug");
        LinuxBug lb1 = new LinuxBug ("echo thread 1 ");
        LinuxBug lb2 = new LinuxBug ("echo thread 2 ");
        lb1.start();
        lb2.start();
   }
}

LinuxBug.c
----------
#include <jni.h>
#include <errno.h>

#ifndef _Included_LinuxBug
#define _Included_LinuxBug^M
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class: LinuxBug
 * Method: systemCall
 * Signature: (Ljava/lang/String;)I
 */
JNIEXPORT jint JNICALL Java_LinuxBug_systemCall
  (JNIEnv *env, jclass class , jstring cmd)
{
        const char *source = (*env)->GetStringUTFChars(env, cmd, 0);
        int res = 0;
        res = system(source);
        if(res != 0) {
                int rest=errno;
                printf ("system return code=%d (%s)\n", res, strerror(rest));
                res = rest;
        }
        (*env)->ReleaseStringUTFChars(env, cmd, source);
        return res;
}
#ifdef __cplusplus
}
#endif
#endif

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
export LD_ASSUME_KERNEL=2.4
(Incident Review ID: 218170)
======================================================================