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8372645: ParallelGC: Remove race between allocation and expansion before is_init_completed

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Reviewed-by: ayang, sjohanss, eosterlund
This commit is contained in:
Axel Boldt-Christmas 2025-12-02 10:58:44 +00:00
parent 7278d2e8e5
commit f636fcadd7
1 changed files with 16 additions and 7 deletions
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23
src/hotspot/share/gc/parallel/parallelScavengeHeap.cpp
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@ -307,9 +307,13 @@ HeapWord* ParallelScavengeHeap::mem_allocate_cas_noexpand(size_t size, bool is_t
HeapWord* ParallelScavengeHeap::mem_allocate_work(size_t size, bool is_tlab) {
for (uint loop_count = 0; /* empty */; ++loop_count) {
HeapWord* result = mem_allocate_cas_noexpand(size, is_tlab);
if (result != nullptr) {
return result;
HeapWord* result;
{
ConditionalMutexLocker locker(Heap_lock, !is_init_completed());
result = mem_allocate_cas_noexpand(size, is_tlab);
if (result != nullptr) {
return result;
}
}
// Read total_collections() under the lock so that multiple
@ -326,10 +330,15 @@ HeapWord* ParallelScavengeHeap::mem_allocate_work(size_t size, bool is_tlab) {
}
if (!is_init_completed()) {
// Can't do GC; try heap expansion to satisfy the request.
result = expand_heap_and_allocate(size, is_tlab);
if (result != nullptr) {
return result;
// Double checked locking, this ensure that is_init_completed() does not
// transition while expanding the heap.
MonitorLocker ml(InitCompleted_lock, Monitor::_no_safepoint_check_flag);
if (!is_init_completed()) {
// Can't do GC; try heap expansion to satisfy the request.
result = expand_heap_and_allocate(size, is_tlab);
if (result != nullptr) {
return result;
}
}
}