8317661: [REDO] store/load order not preserved when handling memory p…

…ool due to weakly ordered memory architecture of aarch64

Reviewed-by: dholmes, aph

src/hotspot/share/code/codeCache.cpp

@@ -573,6 +573,8 @@ CodeBlob* CodeCache::allocate(int size, CodeBlobType code_blob_type, bool handle
         CompileBroker::handle_full_code_cache(orig_code_blob_type);
       }
       return nullptr;
+    } else {
+      OrderAccess::release(); // ensure heap expansion is visible to an asynchronous observer (e.g. CodeHeapPool::get_memory_usage())
     }
     if (PrintCodeCacheExtension) {
       ResourceMark rm;

src/hotspot/share/services/memoryPool.cpp

@@ -179,6 +179,7 @@ CodeHeapPool::CodeHeapPool(CodeHeap* codeHeap, const char* name, bool support_us
 
 MemoryUsage CodeHeapPool::get_memory_usage() {
   size_t used      = used_in_bytes();
+  OrderAccess::acquire(); // ensure possible cache expansion in CodeCache::allocate is seen
   size_t committed = _codeHeap->capacity();
   size_t maxSize   = (available_for_allocation() ? max_size() : 0);