This only happens on Solaris, not on win32, and then only with the JIT enabled.

/home/ovrskeek> printenv JAVA_COMPILER
/home/ovrskeek> java -version
java version "1.2beta4"
Classic VM (build JDK-1.2beta4-K, green threads, sunwjit)
/home/ovrskeek> java LockTest
Time for 1000000 iterations (non recursive) 1490
Segmentation fault (core dumped)
/home/ovrskeek> setenv JAVA_COMPILER NONE
/home/ovrskeek> java LockTest
Time for 1000000 iterations (non recursive) 1890
Exception in thread "main" java.lang.StackOverflowError
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)
        at LockTest.recursiveLock(LockTest.java:28)

[....]

public class LockTest extends Object
{
    static int loopCount = 1000000;
    static String target = "FooBar!";

    public static void main(String[] argv) {
        long t1 = System.currentTimeMillis();
        int i=0;
        while(i<loopCount)
        {
            synchronized(target) {
                i++;
            }
        }
        long t2 = System.currentTimeMillis();
        System.err.println("Time for " + loopCount + " iterations (non recursive) " + (t2-t1));

        t1 = System.currentTimeMillis();
        recursiveLock(loopCount);
        t2 = System.currentTimeMillis();
        System.err.println("Time for " + loopCount + " iterations (recursive, includes method call overhead) " + (t2-t1));
    }

    static synchronized void recursiveLock(int val) {
        if(val == 0)
            return;
        else
            recursiveLock(val-1);
    }
}