src/cpu/x86/vm/frame_x86.cpp

@@ -352,18 +352,21 @@
   // Java frame called from C; skip all C frames and return top C
   // frame of that chunk as the sender
   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 ) {
+  vmassert(jfa->last_Java_pc() != NULL, "not walkable");
     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());
-  return fr;
 }
 
 //------------------------------------------------------------------------------
 // frame::verify_deopt_original_pc
 //

@@ -681,5 +684,23 @@
 // This is a generic constructor which is only used by pns() in debug.cpp.
 frame::frame(void* sp, void* fp, void* pc) {
   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];
+}