diff -r d384f5a5bd0c hotspot/src/share/vm/prims/jni.cpp
--- openjdk/hotspot/src/share/vm/prims/jni.cpp	Mon Aug 06 13:11:51 2007 +0100
+++ openjdk/hotspot/src/share/vm/prims/jni.cpp	Fri Sep 14 09:58:33 2007 +0100
@@ -3209,6 +3209,21 @@ _JNI_IMPORT_OR_EXPORT_ jint JNICALL JNI_
   jint result = JNI_ERR;
   DT_RETURN_MARK(CreateJavaVM, jint, (const jint&)result);
 
+  // We're about to use Atomic::xchg for locking.  On zero platforms
+  // this is implemented using the GCC builtin __sync_lock_test_and_set
+  // which is not guaranteed to do what we're using it for on all
+  // platforms.  So we check it works before doing anything else.
+#if defined(ZERO) && defined(ASSERT)
+  {
+    jint a = 0xCAFEBABE;
+    jint b = Atomic::xchg(0xC0FFEE, &a);
+    void *c = &a;
+    void *d = Atomic::xchg_ptr(&b, &c);
+    assert(a == 0xC0FFEE && b == (jint) 0xCAFEBABE, "Atomic::xchg() works");
+    assert(c == &b && d == &a, "Atomic::xchg_ptr() works");
+  }
+#endif // ZERO & ASSERT
+  
   // At the moment it's only possible to have one Java VM,
   // since some of the runtime state is in global variables.