--- a/hotspot/src/cpu/aarch64/vm/aarch64.ad	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/aarch64.ad	Tue Aug 16 17:31:57 2016 +0100
@@ -4680,7 +4680,7 @@
       Label retaddr;
       __ adr(rscratch2, retaddr);
       __ lea(rscratch1, RuntimeAddress(entry));
-      // Leave a breadcrumb for JavaThread::pd_last_frame().
+      // Leave a breadcrumb for JavaFrameAnchor::capture_last_Java_pc()
       __ stp(zr, rscratch2, Address(__ pre(sp, -2 * wordSize)));
       __ blrt(rscratch1, gpcnt, fpcnt, rtype);
       __ bind(retaddr);

--- a/hotspot/src/cpu/aarch64/vm/c1_Runtime1_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/c1_Runtime1_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -78,7 +78,7 @@
   }
   pop(r0, sp);
 #endif
-  reset_last_Java_frame(true, true);
+  reset_last_Java_frame(true);
   maybe_isb();
 
   // check for pending exceptions
@@ -547,7 +547,7 @@
     __ bind(L);
   }
 #endif
-  __ reset_last_Java_frame(true, false);
+  __ reset_last_Java_frame(true);
   __ maybe_isb();
 
   // check for pending exceptions

--- a/hotspot/src/cpu/aarch64/vm/frame_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/frame_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -336,13 +336,16 @@
   JavaFrameAnchor* jfa = entry_frame_call_wrapper()->anchor();
   assert(!entry_frame_is_first(), "next Java fp must be non zero");
   assert(jfa->last_Java_sp() > sp(), "must be above this frame on stack");
+  // Since we are walking the stack now this nested anchor is obviously walkable
+  // even if it wasn't when it was stacked.
+  if (!jfa->walkable()) {
+    // Capture _last_Java_pc (if needed) and mark anchor walkable.
+    jfa->capture_last_Java_pc();
+  }
   map->clear();
   assert(map->include_argument_oops(), "should be set by clear");
-  if (jfa->last_Java_pc() != NULL ) {
-    frame fr(jfa->last_Java_sp(), jfa->last_Java_fp(), jfa->last_Java_pc());
-    return fr;
-  }
-  frame fr(jfa->last_Java_sp(), jfa->last_Java_fp());
+  vmassert(jfa->last_Java_pc() != NULL, "not walkable");
+  frame fr(jfa->last_Java_sp(), jfa->last_Java_fp(), jfa->last_Java_pc());
   return fr;
 }
 
@@ -769,3 +772,21 @@
   init((intptr_t*)sp, (intptr_t*)fp, (address)pc);
 }
 #endif
+
+void JavaFrameAnchor::make_walkable(JavaThread* thread) {
+  // last frame set?
+  if (last_Java_sp() == NULL) return;
+  // already walkable?
+  if (walkable()) return;
+  vmassert(Thread::current() == (Thread*)thread, "not current thread");
+  vmassert(last_Java_sp() != NULL, "not called from Java code?");
+  vmassert(last_Java_pc() == NULL, "already walkable");
+  capture_last_Java_pc();
+  vmassert(walkable(), "something went wrong");
+}
+
+void JavaFrameAnchor::capture_last_Java_pc() {
+  vmassert(_last_Java_sp != NULL, "no last frame set");
+  vmassert(_last_Java_pc == NULL, "already walkable");
+  _last_Java_pc = (address)_last_Java_sp[-1];
+}

--- a/hotspot/src/cpu/aarch64/vm/interp_masm_aarch64.hpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/interp_masm_aarch64.hpp	Tue Aug 16 17:31:57 2016 +0100
@@ -201,7 +201,7 @@
 // #endif
     MacroAssembler::null_check(reg, offset);
 // #ifdef ASSERT
-//     reset_last_Java_frame(true, false);
+//     reset_last_Java_frame(true);
 // #endif
   }
 

--- a/hotspot/src/cpu/aarch64/vm/javaFrameAnchor_aarch64.hpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/javaFrameAnchor_aarch64.hpp	Tue Aug 16 17:31:57 2016 +0100
@@ -64,10 +64,9 @@
     _last_Java_sp = src->_last_Java_sp;
   }
 
-  // Always walkable
-  bool walkable(void) { return true; }
-  // Never any thing to do since we are always walkable and can find address of return addresses
-  void make_walkable(JavaThread* thread) { }
+  bool walkable(void)                            { return _last_Java_sp != NULL && _last_Java_pc != NULL; }
+  void make_walkable(JavaThread* thread);
+  void capture_last_Java_pc(void);
 
   intptr_t* last_Java_sp(void) const             { return _last_Java_sp; }
 

--- a/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -274,19 +274,18 @@
 }
 
 
-void MacroAssembler::reset_last_Java_frame(bool clear_fp,
-                                           bool clear_pc) {
+void MacroAssembler::reset_last_Java_frame(bool clear_fp) {
   // we must set sp to zero to clear frame
   str(zr, Address(rthread, JavaThread::last_Java_sp_offset()));
+
   // must clear fp, so that compiled frames are not confused; it is
   // possible that we need it only for debugging
   if (clear_fp) {
     str(zr, Address(rthread, JavaThread::last_Java_fp_offset()));
   }
 
-  if (clear_pc) {
-    str(zr, Address(rthread, JavaThread::last_Java_pc_offset()));
-  }
+  // Always clear the pc because it could have been set by make_walkable()
+  str(zr, Address(rthread, JavaThread::last_Java_pc_offset()));
 }
 
 // Calls to C land
@@ -632,7 +631,7 @@
 
   // reset last Java frame
   // Only interpreter should have to clear fp
-  reset_last_Java_frame(true, true);
+  reset_last_Java_frame(true);
 
    // C++ interp handles this in the interpreter
   check_and_handle_popframe(java_thread);
@@ -875,7 +874,7 @@
   if (type == bytecode_start) {
     // set_last_Java_frame(esp, rfp, (address)NULL);
     Assembler:: notify(type);
-    // reset_last_Java_frame(true, false);
+    // reset_last_Java_frame(true);
   }
   else
     Assembler:: notify(type);

--- a/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.hpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/macroAssembler_aarch64.hpp	Tue Aug 16 17:31:57 2016 +0100
@@ -757,10 +757,10 @@
                            Register last_java_pc,
                            Register scratch);
 
-  void reset_last_Java_frame(Register thread, bool clearfp, bool clear_pc);
+  void reset_last_Java_frame(Register thread);
 
-  // thread in the default location (r15_thread on 64bit)
-  void reset_last_Java_frame(bool clear_fp, bool clear_pc);
+  // thread in the default location (rthread)
+  void reset_last_Java_frame(bool clear_fp);
 
   // Stores
   void store_check(Register obj);                // store check for obj - register is destroyed afterwards

--- a/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/sharedRuntime_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -2030,7 +2030,7 @@
     __ bind(dtrace_method_exit_done);
   }
 
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
 
   // Unpack oop result
   if (ret_type == T_OBJECT || ret_type == T_ARRAY) {
@@ -2370,7 +2370,7 @@
     __ bind(retaddr);
     oop_maps->add_gc_map( __ pc()-start, map->deep_copy());
 
-    __ reset_last_Java_frame(false, false);
+    __ reset_last_Java_frame(false);
 
     __ b(after_fetch_unroll_info_call);
   } // EnableJVMCI
@@ -2465,7 +2465,7 @@
   // find any register it might need.
   oop_maps->add_gc_map(__ pc() - start, map);
 
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
 
 #if INCLUDE_JVMCI
   if (EnableJVMCI) {
@@ -2606,7 +2606,7 @@
                        new OopMap( frame_size_in_words, 0 ));
 
   // Clear fp AND pc
-  __ reset_last_Java_frame(true, true);
+  __ reset_last_Java_frame(true);
 
   // Collect return values
   __ ldrd(v0, Address(sp, RegisterSaver::v0_offset_in_bytes()));
@@ -2709,7 +2709,7 @@
 
   oop_maps->add_gc_map(__ pc() - start, map);
 
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
 
   // move UnrollBlock* into r4
   __ mov(r4, r0);
@@ -2828,7 +2828,7 @@
   oop_maps->add_gc_map(the_pc - start, new OopMap(SimpleRuntimeFrame::framesize, 0));
 
   // Clear fp AND pc
-  __ reset_last_Java_frame(true, true);
+  __ reset_last_Java_frame(true);
 
   // Pop self-frame.
   __ leave();                 // Epilog
@@ -2906,7 +2906,7 @@
 
   Label noException;
 
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
 
   __ maybe_isb();
   __ membar(Assembler::LoadLoad | Assembler::LoadStore);
@@ -2985,7 +2985,7 @@
   // r0 contains the address we are going to jump to assuming no exception got installed
 
   // clear last_Java_sp
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
   // check for pending exceptions
   Label pending;
   __ ldr(rscratch1, Address(rthread, Thread::pending_exception_offset()));
@@ -3116,7 +3116,7 @@
 
   oop_maps->add_gc_map(the_pc - start, new OopMap(SimpleRuntimeFrame::framesize, 0));
 
-  __ reset_last_Java_frame(false, true);
+  __ reset_last_Java_frame(false);
 
   // Restore callee-saved registers
 

--- a/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/stubGenerator_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -3801,7 +3801,7 @@
 
     oop_maps->add_gc_map(the_pc - start, map);
 
-    __ reset_last_Java_frame(true, true);
+    __ reset_last_Java_frame(true);
     __ maybe_isb();
 
     __ leave();

--- a/hotspot/src/cpu/aarch64/vm/templateInterpreterGenerator_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/cpu/aarch64/vm/templateInterpreterGenerator_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -1353,7 +1353,7 @@
   __ stlrw(rscratch1, rscratch2);
 
   // reset_last_Java_frame
-  __ reset_last_Java_frame(true, true);
+  __ reset_last_Java_frame(true);
 
   // reset handle block
   __ ldr(t, Address(rthread, JavaThread::active_handles_offset()));

--- a/hotspot/src/os_cpu/linux_aarch64/vm/thread_linux_aarch64.cpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/os_cpu/linux_aarch64/vm/thread_linux_aarch64.cpp	Tue Aug 16 17:31:57 2016 +0100
@@ -47,7 +47,7 @@
 
   // If we have a last_Java_frame, then we should use it even if
   // isInJava == true.  It should be more reliable than ucontext info.
-  if (jt->has_last_Java_frame()) {
+  if (jt->has_last_Java_frame() && jt->frame_anchor()->walkable()) {
     *fr_addr = jt->pd_last_frame();
     return true;
   }

--- a/hotspot/src/os_cpu/linux_aarch64/vm/thread_linux_aarch64.hpp	Mon Aug 15 14:08:01 2016 -0700
+++ b/hotspot/src/os_cpu/linux_aarch64/vm/thread_linux_aarch64.hpp	Tue Aug 16 17:31:57 2016 +0100
@@ -43,12 +43,7 @@
 
   frame pd_last_frame() {
     assert(has_last_Java_frame(), "must have last_Java_sp() when suspended");
-    if (_anchor.last_Java_pc() != NULL) {
-      return frame(_anchor.last_Java_sp(), _anchor.last_Java_fp(), _anchor.last_Java_pc());
-    } else {
-      // This will pick up pc from sp
-      return frame(_anchor.last_Java_sp(), _anchor.last_Java_fp());
-    }
+    return frame(_anchor.last_Java_sp(), _anchor.last_Java_fp(), _anchor.last_Java_pc());
   }
 
  public: