7033292: G1: nightly failure: Non-dirty cards in region that should be dirty
Summary: The epochs on the card cache array are initialized to 0 and our initial epoch also starts at 0. So, until the first GC, it might be possible to successfully "claim" a card which was in fact never initialized.
Reviewed-by: johnc, iveresov, ysr
--- a/hotspot/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp Wed Mar 30 10:26:59 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp Mon Apr 04 13:18:35 2011 -0400
@@ -51,7 +51,11 @@
_cache_size_index(0), _expand_card_counts(false),
_hot_cache(NULL),
_def_use_cache(false), _use_cache(false),
- _n_periods(0),
+ // We initialize the epochs of the array to 0. By initializing
+ // _n_periods to 1 and not 0 we automatically invalidate all the
+ // entries on the array. Otherwise we might accidentally think that
+ // we claimed a card that was in fact never set (see CR7033292).
+ _n_periods(1),
_threads(NULL), _n_threads(0)
{