1.1 --- a/src/share/vm/memory/blockOffsetTable.hpp Thu Apr 22 13:23:15 2010 -0700
1.2 +++ b/src/share/vm/memory/blockOffsetTable.hpp Mon May 03 10:24:51 2010 -0700
1.3 @@ -140,14 +140,38 @@
1.4 "right address out of range");
1.5 assert(left < right, "Heap addresses out of order");
1.6 size_t num_cards = pointer_delta(right, left) >> LogN_words;
1.7 - memset(&_offset_array[index_for(left)], offset, num_cards);
1.8 +
1.9 + // Below, we may use an explicit loop instead of memset()
1.10 + // because on certain platforms memset() can give concurrent
1.11 + // readers "out-of-thin-air," phantom zeros; see 6948537.
1.12 + if (UseMemSetInBOT) {
1.13 + memset(&_offset_array[index_for(left)], offset, num_cards);
1.14 + } else {
1.15 + size_t i = index_for(left);
1.16 + const size_t end = i + num_cards;
1.17 + for (; i < end; i++) {
1.18 + _offset_array[i] = offset;
1.19 + }
1.20 + }
1.21 }
1.22
1.23 void set_offset_array(size_t left, size_t right, u_char offset) {
1.24 assert(right < _vs.committed_size(), "right address out of range");
1.25 assert(left <= right, "indexes out of order");
1.26 size_t num_cards = right - left + 1;
1.27 - memset(&_offset_array[left], offset, num_cards);
1.28 +
1.29 + // Below, we may use an explicit loop instead of memset
1.30 + // because on certain platforms memset() can give concurrent
1.31 + // readers "out-of-thin-air," phantom zeros; see 6948537.
1.32 + if (UseMemSetInBOT) {
1.33 + memset(&_offset_array[left], offset, num_cards);
1.34 + } else {
1.35 + size_t i = left;
1.36 + const size_t end = i + num_cards;
1.37 + for (; i < end; i++) {
1.38 + _offset_array[i] = offset;
1.39 + }
1.40 + }
1.41 }
1.42
1.43 void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const {
