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8380562: GenShen: GC notification event may see invalid values

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Reviewed-by: cslucas, kdnilsen
This commit is contained in:
William Kemper 2026-03-20 23:42:08 +00:00
parent 137d97131b
commit d610aceed4
3 changed files with 14 additions and 33 deletions
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5
src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
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@ -2700,10 +2700,7 @@ GrowableArray<MemoryPool*> ShenandoahHeap::memory_pools() {
}
MemoryUsage ShenandoahHeap::memory_usage() {
assert(_initial_size <= ShenandoahHeap::heap()->max_capacity(), "sanity");
assert(used() <= ShenandoahHeap::heap()->max_capacity(), "sanity");
assert(committed() <= ShenandoahHeap::heap()->max_capacity(), "sanity");
return MemoryUsage(_initial_size, used(), committed(), max_capacity());
return shenandoah_memory_usage(_initial_size, used(), committed(), max_capacity());
}
ShenandoahRegionIterator::ShenandoahRegionIterator() :

31
src/hotspot/share/gc/shenandoah/shenandoahMemoryPool.cpp
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@ -48,25 +48,7 @@ ShenandoahMemoryPool::ShenandoahMemoryPool(ShenandoahHeap* heap,
MemoryUsage ShenandoahMemoryPool::get_memory_usage() {
size_t initial = initial_size();
size_t max = max_size();
size_t used = used_in_bytes();
size_t committed = _heap->committed();
// These asserts can never fail: max is stable, and all updates to other values never overflow max.
assert(initial <= max, "initial: %zu, max: %zu", initial, max);
assert(used <= max, "used: %zu, max: %zu", used, max);
assert(committed <= max, "committed: %zu, max: %zu", committed, max);
// Committed and used are updated concurrently and independently. They can momentarily break
// the assert below, which would also fail in downstream code. To avoid that, adjust values
// to make sense under the race. See JDK-8207200.
committed = MAX2(used, committed);
assert(used <= committed, "used: %zu, committed: %zu", used, committed);
assert(initial <= _heap->max_capacity(), "sanity");
assert(committed <= _heap->max_capacity(), "sanity");
assert(max <= _heap->max_capacity(), "sanity");
return MemoryUsage(initial, used, committed, max);
return shenandoah_memory_usage(initial_size(), used_in_bytes(), _heap->committed(), max_size());
}
size_t ShenandoahMemoryPool::used_in_bytes() {
@ -83,16 +65,7 @@ ShenandoahGenerationalMemoryPool::ShenandoahGenerationalMemoryPool(ShenandoahHea
_generation(generation) { }
MemoryUsage ShenandoahGenerationalMemoryPool::get_memory_usage() {
size_t initial = initial_size();
size_t max = max_size();
size_t used = used_in_bytes();
size_t committed = _generation->used_regions_size();
assert(initial <= _heap->max_capacity(), "sanity");
assert(used <= _heap->max_capacity(), "sanity");
assert(committed <= _heap->max_capacity(), "sanity");
assert(max <= _heap->max_capacity(), "sanity");
return MemoryUsage(initial, used, committed, max);
return shenandoah_memory_usage(initial_size(), used_in_bytes(), _generation->used_regions_size(), max_size());
}
size_t ShenandoahGenerationalMemoryPool::used_in_bytes() {

11
src/hotspot/share/gc/shenandoah/shenandoahMemoryPool.hpp
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@ -30,6 +30,17 @@
#include "services/memoryPool.hpp"
#include "services/memoryUsage.hpp"
// Constructs a MemoryUsage from concurrently sampled values, clamping committed
// to be at least as large as used to account for concurrent updates. See JDK-8207200.
inline MemoryUsage shenandoah_memory_usage(size_t initial, size_t used, size_t committed, size_t max) {
assert(initial <= max, "initial: %zu, max: %zu", initial, max);
assert(used <= max, "used: %zu, max: %zu", used, max);
assert(committed <= max, "committed: %zu, max: %zu", committed, max);
committed = MAX2(used, committed);
assert(used <= committed, "used: %zu, committed: %zu", used, committed);
return MemoryUsage(initial, used, committed, max);
}
class ShenandoahMemoryPool : public CollectedMemoryPool {
protected:
ShenandoahHeap* _heap;