Mercurial > hg > openjdk > jdk8u > hotspot
changeset 9415:bc32046eef89
8259271: gc/parallel/TestDynShrinkHeap.java still fails "assert(covered_region.contains(new_memregion)) failed: new region is not in covered_region"
Summary: Use load_acquire to order reads of top and end.
Reviewed-by: tschatzl, iwalulya, eosterlund
| author | kbarrett |
|---|---|
| date | Fri, 22 Jan 2021 11:20:52 +0000 |
| parents | 6f024d171932 |
| children | a4312636c0f7 |
| files | src/share/vm/gc_implementation/shared/mutableSpace.cpp |
| diffstat | 1 files changed, 6 insertions(+), 1 deletions(-) [+] |
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--- a/src/share/vm/gc_implementation/shared/mutableSpace.cpp Thu Dec 17 14:18:00 2020 +0000 +++ b/src/share/vm/gc_implementation/shared/mutableSpace.cpp Fri Jan 22 11:20:52 2021 +0000 @@ -28,6 +28,7 @@ #include "gc_implementation/shared/mutableSpace.hpp" #include "gc_implementation/shared/spaceDecorator.hpp" #include "oops/oop.inline.hpp" +#include "runtime/orderAccess.hpp" #include "runtime/safepoint.hpp" #include "runtime/thread.hpp" #endif // INCLUDE_ALL_GCS @@ -192,7 +193,11 @@ // This version is lock-free. HeapWord* MutableSpace::cas_allocate(size_t size) { do { - HeapWord* obj = top(); + // Read top before end, else the range check may pass when it shouldn't. + // If end is read first, other threads may advance end and top such that + // current top > old end and current top + size > current end. Then + // pointer_delta underflows, allowing installation of top > current end. + HeapWord* obj = (HeapWord*)OrderAccess::load_ptr_acquire(top_addr()); if (pointer_delta(end(), obj) >= size) { HeapWord* new_top = obj + size; HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);