From bc7497dce05dc78399ce27a3a5d8c3fd43bfb1d0 Mon Sep 17 00:00:00 2001
From: johnc <unknown>
Date: Wed, 7 Apr 2010 11:43:53 -0700
Subject: [PATCH] 6940894: G1: assert(new_obj != 0 || ... "should be
 forwarded") for compaction tests Summary: Humongous regions may contain
 multiple objects as a result of being retained as to-space from a previous GC
 and then re-used as to-space after being tagged as humongous. These changes
 include a check that causes retained to-space regions that are now tagged as
 humongous to be disregarded and a new to-space region allocated. Reviewed-by:
 tonyp, iveresov

---
 .../gc_implementation/g1/g1CollectedHeap.cpp  | 20 +++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
index 73d269895..1734fe0ba 100644
--- a/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
+++ b/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
@@ -2942,6 +2942,9 @@ void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
   // the same region
   assert(r == NULL || !r->is_gc_alloc_region(),
          "shouldn't already be a GC alloc region");
+  assert(r == NULL || !r->isHumongous(),
+         "humongous regions shouldn't be used as GC alloc regions");
+
   HeapWord* original_top = NULL;
   if (r != NULL)
     original_top = r->top();
@@ -3084,12 +3087,17 @@ void G1CollectedHeap::get_gc_alloc_regions() {
 
       if (alloc_region->in_collection_set() ||
           alloc_region->top() == alloc_region->end() ||
-          alloc_region->top() == alloc_region->bottom()) {
-        // we will discard the current GC alloc region if it's in the
-        // collection set (it can happen!), if it's already full (no
-        // point in using it), or if it's empty (this means that it
-        // was emptied during a cleanup and it should be on the free
-        // list now).
+          alloc_region->top() == alloc_region->bottom() ||
+          alloc_region->isHumongous()) {
+        // we will discard the current GC alloc region if
+        // * it's in the collection set (it can happen!),
+        // * it's already full (no point in using it),
+        // * it's empty (this means that it was emptied during
+        // a cleanup and it should be on the free list now), or
+        // * it's humongous (this means that it was emptied
+        // during a cleanup and was added to the free list, but
+        // has been subseqently used to allocate a humongous
+        // object that may be less than the region size).
 
         alloc_region = NULL;
       }
-- 
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