--- a/hotspot/src/os/bsd/vm/os_bsd.cpp	Wed Jun 05 09:47:27 2013 -0700
+++ b/hotspot/src/os/bsd/vm/os_bsd.cpp	Thu Jun 06 05:56:33 2013 -0700
@@ -3030,6 +3030,19 @@
     sigAct.sa_sigaction = signalHandler;
     sigAct.sa_flags = SA_SIGINFO|SA_RESTART;
   }
+#if __APPLE__
+  // Needed for main thread as XNU (Mac OS X kernel) will only deliver SIGSEGV
+  // (which starts as SIGBUS) on main thread with faulting address inside "stack+guard pages"
+  // if the signal handler declares it will handle it on alternate stack.
+  // Notice we only declare we will handle it on alt stack, but we are not
+  // actually going to use real alt stack - this is just a workaround.
+  // Please see ux_exception.c, method catch_mach_exception_raise for details
+  // link http://www.opensource.apple.com/source/xnu/xnu-2050.18.24/bsd/uxkern/ux_exception.c
+  if (sig == SIGSEGV) {
+    sigAct.sa_flags |= SA_ONSTACK;
+  }
+#endif
+
   // Save flags, which are set by ours
   assert(sig > 0 && sig < MAXSIGNUM, "vm signal out of expected range");
   sigflags[sig] = sigAct.sa_flags;

--- a/hotspot/src/share/vm/runtime/thread.hpp	Wed Jun 05 09:47:27 2013 -0700
+++ b/hotspot/src/share/vm/runtime/thread.hpp	Thu Jun 06 05:56:33 2013 -0700
@@ -638,9 +638,6 @@
   jint _hashStateZ ;
   void * _schedctl ;
 
-  intptr_t _ScratchA, _ScratchB ;              // Scratch locations for fast-path sync code
-  static ByteSize ScratchA_offset()            { return byte_offset_of(Thread, _ScratchA ); }
-  static ByteSize ScratchB_offset()            { return byte_offset_of(Thread, _ScratchB ); }
 
   volatile jint rng [4] ;                      // RNG for spin loop