Problem: Initializing a Java VM "steals" stack space from other
threads. It basically renders JNI unusable in any non-trivial way. The
problem occurs on Solaris 8/10 on either sparc/x86. A test program is
included to demonstrate the problem.

Java Version:

>> java -version java version "1.5.0_02" Java(TM) 2 Runtime Environment,

Standard Edition (build 1.5.0_02-b09) Java HotSpot(TM) Server VM (build
1.5.0_02-b09, mixed mode)

This program demonstrates that initializing a Java VM "steals"
  * stack space from other threads.
  * For instance, in the sample output below, before initializing the
  * JVM, the application has used up 1.8M of stack space. But after
  * initializing the JVM, the main thread's allocated stack space has
  * shrunk to just the single 488K block at 0xFFB76000! That means
  * that the main thread can never again exceed 488K of stack, or else
  * the program will crash.

  Stack starts near 0xffbeef10

  Initial stack:
  FF3A0000 176K read/exec /usr/lib/ld.so.1
  FF3DC000 8K read/write/exec /usr/lib/ld.so.1
  FF3DE000 8K read/write/exec /usr/lib/ld.so.1
  FFBEC000 16K read/write/exec [ stack ]
   total 7352K

  recurse() stack near 0xffa1a2ec

  Stack after recurse(20000):
  FF3A0000 176K read/exec /usr/lib/ld.so.1
  FF3DC000 8K read/write/exec /usr/lib/ld.so.1
  FF3DE000 8K read/write/exec /usr/lib/ld.so.1
  FFA18000 1888K read/write/exec [ stack ]
   total 9224K

   Stack after jvm:
   FF3A0000 176K read/exec /usr/lib/ld.so.1
   FF3DC000 8K read/write/exec /usr/lib/ld.so.1
   FF3DE000 8K read/write/exec /usr/lib/ld.so.1
   FFA18000 1376K read/write/exec [ stack ]
   FFB70000 24K - [ stack ]
   FFB76000 488K read/write/exec [ stack ]
    total 82304K

To compile:

solaris sparc:
   cc -g -I/usr/local/java/jdk/include
-I/usr/local/java/jdk/include/solaris
-L/usr/local/java/jdk/jre/lib/sparc -R/usr/local/java/jdk/jre/lib/sparc
-ljvm -lpthread stack.c

solaris x86:
   cc -g -I/usr/local/java/jdk/include
-I/usr/local/java/jdk/include/solaris -L/usr/local/java/jdk/jre/lib/i386
-R/usr/local/java/jdk/jre/lib/i386 -ljvm -lpthread stack.c

linux:
   gcc -g -I/usr/local/java/jdk/include
-I/usr/local/java/jdk/include/linux
-L/usr/local/java/jdk/jre/lib/i386/server
-Wl,-rpath,/usr/local/java/jdk/jre/lib/i386/server -ljvm -lpthread stack.c
  */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <jni.h>

void recurse(int n)
{
     if (n > 0) {
  recurse(n-1);
     } else {
  printf("recurse() stack near 0x%x\n", &n);
     }
}

void pmap()
{
     /* check if we have gnu grep installed */
     int ret = system("echo hi | gnu grep -1 hi > /dev/null 2>&1");
     char buf[BUFSIZ];
     if (ret == 0) {
  snprintf(buf, sizeof(buf), "pmap %d | gnu grep -3 stack", getpid());
     } else {
  snprintf(buf, sizeof(buf), "pmap %d | grep stack", getpid());
     }
     system(buf);
}

void jvm()
{
     JavaVMInitArgs vm_args;
     vm_args.version = JNI_VERSION_1_4;
     vm_args.nOptions = 0;
     JNI_GetDefaultJavaVMInitArgs(&vm_args);
     JavaVM *jvm;
     JNIEnv *env;
     long result = JNI_CreateJavaVM(&jvm, (void **)&env, &vm_args);
     if (result == JNI_ERR) {
  fprintf(stderr, "ERROR initializing the JVM\n");
  exit(1);
     }
}

int main(int argc, char **argv)
{
     int x;
     printf("Stack starts near 0x%x\n", &x);
     printf("\nInitial stack:\n");
     pmap();
     printf("\n");

     int n = 20000;
#ifdef __linux
     /* linux appears to give you a larger initial stack */
     n = 100000;
#endif
     if (argc >= 2) {
  n = atoi(argv[1]);
     }
     recurse(n);

     printf("\nStack after recurse(%d):\n", n);
     pmap();

     jvm();

     printf("\nStack after jvm:\n");
     pmap();

     printf("\nPrepare to crash:\n");
     recurse(n*2);

     printf("\nWOOHOO! No crash!\n");
}
###@###.### 2005-05-12 19:57:37 GMT