src/hotspot/share/gc/shenandoah/shenandoahForwarding.inline.hpp

rev 58162 : 8237632: Shenandoah fails some vmTestbase_nsk_jvmti tests with "Forwardee must point to a heap address"

*** 26,47 ****
  #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
  
  #include "gc/shenandoah/shenandoahAsserts.hpp"
  #include "gc/shenandoah/shenandoahForwarding.hpp"
  #include "oops/markWord.inline.hpp"
  
  inline HeapWord* ShenandoahForwarding::get_forwardee_raw(oop obj) {
    shenandoah_assert_in_heap(NULL, obj);
    return get_forwardee_raw_unchecked(obj);
  }
  
  inline HeapWord* ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
    markWord mark = obj->mark_raw();
    if (mark.is_marked()) {
!     return (HeapWord*) mark.clear_lock_bits().to_pointer();
!   } else {
      return cast_from_oop<HeapWord*>(obj);
    }
  }
  
  inline oop ShenandoahForwarding::get_forwardee(oop obj) {
    shenandoah_assert_correct(NULL, obj);
--- 26,69 ----
  #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
  
  #include "gc/shenandoah/shenandoahAsserts.hpp"
  #include "gc/shenandoah/shenandoahForwarding.hpp"
  #include "oops/markWord.inline.hpp"
+ #include "runtime/thread.hpp"
  
  inline HeapWord* ShenandoahForwarding::get_forwardee_raw(oop obj) {
    shenandoah_assert_in_heap(NULL, obj);
    return get_forwardee_raw_unchecked(obj);
  }
  
  inline HeapWord* ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
+   // JVMTI and JFR code use mark words for marking objects for their needs.
+   // On this path, we can encounter the "marked" object, but with NULL
+   // fwdptr. That object is still not forwarded, and we need to return
+   // the object itself.
    markWord mark = obj->mark_raw();
    if (mark.is_marked()) {
!     HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
!     if (fwdptr != NULL) {
!       return fwdptr;
!     }
!   }
    return cast_from_oop<HeapWord*>(obj);
+ }
+ 
+ inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) {
+   // Same as above, but mutator thread cannot ever see NULL forwardee.
+   shenandoah_assert_correct(NULL, obj);
+   assert(Thread::current()->is_Java_thread(), "Must be a mutator thread");
+ 
+   markWord mark = obj->mark_raw();
+   if (mark.is_marked()) {
+     HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
+     assert(fwdptr != NULL, "Forwarding pointer is never null here");
+     return cast_to_oop(fwdptr);
+   } else {
+     return obj;
    }
  }
  
  inline oop ShenandoahForwarding::get_forwardee(oop obj) {
    shenandoah_assert_correct(NULL, obj);