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8225716: G1 GC: Undefined behaviour in G1BlockOffsetTablePart::block_at_or_preceding

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Reviewed-by: kbarrett, tschatzl
This commit is contained in:
Andrew Haley 2019-06-18 16:15:15 +01:00
parent fe66fd327f
commit 41ca20f5b5
3 changed files with 10 additions and 13 deletions
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6
src/hotspot/share/gc/g1/g1BlockOffsetTable.cpp
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@ -391,8 +391,6 @@ G1BlockOffsetTablePart::print_on(outputStream* out) {
#endif // !PRODUCT #endif // !PRODUCT
HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() { HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
"just checking");
_next_offset_index = _bot->index_for_raw(_space->bottom()); _next_offset_index = _bot->index_for_raw(_space->bottom());
_next_offset_index++; _next_offset_index++;
_next_offset_threshold = _next_offset_threshold =
@ -401,8 +399,6 @@ HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() {
} }
void G1BlockOffsetTablePart::zero_bottom_entry_raw() { void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
"just checking");
size_t bottom_index = _bot->index_for_raw(_space->bottom()); size_t bottom_index = _bot->index_for_raw(_space->bottom());
assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(), assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(),
"Precondition of call"); "Precondition of call");
@ -410,8 +406,6 @@ void G1BlockOffsetTablePart::zero_bottom_entry_raw() {
} }
HeapWord* G1BlockOffsetTablePart::initialize_threshold() { HeapWord* G1BlockOffsetTablePart::initialize_threshold() {
assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array),
"just checking");
_next_offset_index = _bot->index_for(_space->bottom()); _next_offset_index = _bot->index_for(_space->bottom());
_next_offset_index++; _next_offset_index++;
_next_offset_threshold = _next_offset_threshold =

7
src/hotspot/share/gc/g1/g1BlockOffsetTable.hpp
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@ -52,7 +52,7 @@ private:
// Array for keeping offsets for retrieving object start fast given an // Array for keeping offsets for retrieving object start fast given an
// address. // address.
u_char* _offset_array; // byte array keeping backwards offsets volatile u_char* _offset_array; // byte array keeping backwards offsets
void check_offset(size_t offset, const char* msg) const { void check_offset(size_t offset, const char* msg) const {
assert(offset <= BOTConstants::N_words, assert(offset <= BOTConstants::N_words,
@ -64,10 +64,7 @@ private:
// For performance these have to devolve to array accesses in product builds. // For performance these have to devolve to array accesses in product builds.
inline u_char offset_array(size_t index) const; inline u_char offset_array(size_t index) const;
void set_offset_array_raw(size_t index, u_char offset) { inline void set_offset_array_raw(size_t index, u_char offset);
_offset_array[index] = offset;
}
inline void set_offset_array(size_t index, u_char offset); inline void set_offset_array(size_t index, u_char offset);
inline void set_offset_array(size_t index, HeapWord* high, HeapWord* low); inline void set_offset_array(size_t index, HeapWord* high, HeapWord* low);

10
src/hotspot/share/gc/g1/g1BlockOffsetTable.inline.hpp
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@ -29,6 +29,7 @@
#include "gc/g1/heapRegion.hpp" #include "gc/g1/heapRegion.hpp"
#include "gc/shared/memset_with_concurrent_readers.hpp" #include "gc/shared/memset_with_concurrent_readers.hpp"
#include "gc/shared/space.hpp" #include "gc/shared/space.hpp"
#include "runtime/atomic.hpp"
inline HeapWord* G1BlockOffsetTablePart::block_start(const void* addr) { inline HeapWord* G1BlockOffsetTablePart::block_start(const void* addr) {
if (addr >= _space->bottom() && addr < _space->end()) { if (addr >= _space->bottom() && addr < _space->end()) {
@ -51,7 +52,11 @@ inline HeapWord* G1BlockOffsetTablePart::block_start_const(const void* addr) con
u_char G1BlockOffsetTable::offset_array(size_t index) const { u_char G1BlockOffsetTable::offset_array(size_t index) const {
check_index(index, "index out of range"); check_index(index, "index out of range");
return _offset_array[index]; return Atomic::load(&_offset_array[index]);
}
void G1BlockOffsetTable::set_offset_array_raw(size_t index, u_char offset) {
Atomic::store(offset, &_offset_array[index]);
} }
void G1BlockOffsetTable::set_offset_array(size_t index, u_char offset) { void G1BlockOffsetTable::set_offset_array(size_t index, u_char offset) {
@ -71,7 +76,8 @@ void G1BlockOffsetTable::set_offset_array(size_t left, size_t right, u_char offs
check_index(right, "right index out of range"); check_index(right, "right index out of range");
assert(left <= right, "indexes out of order"); assert(left <= right, "indexes out of order");
size_t num_cards = right - left + 1; size_t num_cards = right - left + 1;
memset_with_concurrent_readers(&_offset_array[left], offset, num_cards); memset_with_concurrent_readers
(const_cast<u_char*> (&_offset_array[left]), offset, num_cards);
} }
// Variant of index_for that does not check the index for validity. // Variant of index_for that does not check the index for validity.