RFR 8225573: Shenandoah: Enhance ShenandoahVerifier to ensure roots to-space invariant

[Aleksey Shipilev]

On 6/18/19 6:57 PM, Zhengyu Gu wrote:
> On 6/11/19 1:21 PM, Zhengyu Gu wrote:
>> This patch adds a new API to Shenandoah verifier, the verifies all roots only contain to-space
>> references. This API should help concurrent root processing work, to catch bad references in roots.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8225573
>> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8225573/webrev.00/8225573
> 
> Sorry, bad link. Should be:
> 
> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8225573/webrev.00/

Looks okay.

*) The mix of SA::assert_* and SA::print_failure irritates me. I think it is cleaner to stick with
one way of doing things. "assert" kinda implies in can be turned off (even though it does not in
this case). For example:

class ShenandoahVerifyInToSpaceClosure : public OopClosure {
private:
  template <class T>
  void do_oop_work(T* p) {
    T o = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(o)) {
      oop obj = CompressedOops::decode_not_null(o);

      ShenandoahHeap* heap = ShenandoahHeap::heap_no_check();

      if (!heap->marking_context()->is_marked(obj)) {
        ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
                "Verify Roots In To-Space", "Should be marked", __FILE__, __LINE__);
      }

      if (heap->in_collection_set(obj)) {
        ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
                "Verify Roots In To-Space", "Should not be in collection set", __FILE__, __LINE__);
      }

      oop fwd = (oop) ShenandoahForwarding::get_forwardee_raw_unchecked(obj);
      if (!oopDesc::equals_raw(obj, fwd)) {
        ShenandoahAsserts::print_failure(ShenandoahAsserts::_safe_all, obj, p, NULL,
                "Verify Roots In To-Space", "Should not be forwarded", __FILE__, __LINE__);
      }
    }
  }

-Aleksey

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