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6952853: SIGSEGV with UseAdaptiveGCBoundary on 64b linux running jvm2008

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Shrinking of a generation and the corresponding card table was causing part of the card table to be uncommitted.

Reviewed-by: jcoomes
This commit is contained in:
Jon Masamitsu 2010-06-23 08:35:31 -07:00
parent 428d02d5d7
commit c443776640
3 changed files with 54 additions and 17 deletions
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37
hotspot/src/share/vm/memory/cardTableModRefBS.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2000, 2009, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -284,12 +284,19 @@ void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
committed_unique_to_self(ind, MemRegion(new_end_aligned,
cur_committed.end()));
if (!uncommit_region.is_empty()) {
if (!os::uncommit_memory((char*)uncommit_region.start(),
uncommit_region.byte_size())) {
assert(false, "Card table contraction failed");
// The call failed so don't change the end of the
// committed region. This is better than taking the
// VM down.
// It is not safe to uncommit cards if the boundary between
// the generations is moving. A shrink can uncommit cards
// owned by generation A but being used by generation B.
if (!UseAdaptiveGCBoundary) {
if (!os::uncommit_memory((char*)uncommit_region.start(),
uncommit_region.byte_size())) {
assert(false, "Card table contraction failed");
// The call failed so don't change the end of the
// committed region. This is better than taking the
// VM down.
new_end_aligned = _committed[ind].end();
}
} else {
new_end_aligned = _committed[ind].end();
}
}
@ -297,6 +304,19 @@ void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
// In any case, we can reset the end of the current committed entry.
_committed[ind].set_end(new_end_aligned);
#ifdef ASSERT
// Check that the last card in the new region is committed according
// to the tables.
bool covered = false;
for (int cr = 0; cr < _cur_covered_regions; cr++) {
if (_committed[cr].contains(new_end - 1)) {
covered = true;
break;
}
}
assert(covered, "Card for end of new region not committed");
#endif
// The default of 0 is not necessarily clean cards.
jbyte* entry;
if (old_region.last() < _whole_heap.start()) {
@ -354,6 +374,9 @@ void CardTableModRefBS::resize_covered_region(MemRegion new_region) {
addr_for((jbyte*) _committed[ind].start()),
addr_for((jbyte*) _committed[ind].last()));
}
// Touch the last card of the covered region to show that it
// is committed (or SEGV).
debug_only(*byte_for(_covered[ind].last());)
debug_only(verify_guard();)
}