RFR (XS) 8224880: ShenandoahRootScanner::roots_do assert is too strong

[Aleksey Shipilev]

Bug:
  https://bugs.openjdk.java.net/browse/JDK-8224970

It reliably happens with x86_32 and gc/shenandoah/oom tests that enter the heap inspection on OOM.
That operation is done under its own VM op. So, the fix is to relax the assert to accept
non-Shenandoah safepoints.

diff -r 785a12e0f89b src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.inline.hpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.inline.hpp        Wed May 29 12:01:21
2019 +0200
+++ b/src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.inline.hpp        Wed May 29 12:57:03
2019 +0200
@@ -28,4 +28,5 @@
 #include "gc/shenandoah/shenandoahRootProcessor.hpp"
 #include "gc/shenandoah/shenandoahTimingTracker.hpp"
+#include "gc/shenandoah/shenandoahUtils.hpp"
 #include "memory/resourceArea.hpp"

@@ -91,7 +92,8 @@
 template <typename ITR>
 void ShenandoahRootScanner<ITR>::roots_do(uint worker_id, OopClosure* oops, CLDClosure* clds,
CodeBlobClosure* code, ThreadClosure *tc) {
-  assert(!ShenandoahHeap::heap()->unload_classes() ||
+  assert(!ShenandoahSafepoint::is_at_shenandoah_safepoint() ||
+         !ShenandoahHeap::heap()->unload_classes() ||
           ShenandoahHeap::heap()->heuristics()->can_do_traversal_gc(),
-          "No class unloading or traversal GC");
+          "Expect class unloading or traversal when Shenandoah cycle is running");
   ShenandoahParallelOopsDoThreadClosure tc_cl(oops, code, tc);
   ResourceMark rm;


Testing: hotspot_gc_shenandoah + failing test

-- 
Thanks,
-Aleksey