src/share/vm/oops/constantPool.cpp

rev 6875 : 8056240: Investigate increased GC remark time after class unloading changes in CRM Fuse
Reviewed-by: mgerdin, coleenp, bdelsart

@@ -1815,15 +1815,26 @@
 #undef DBG
 
 
 void ConstantPool::set_on_stack(const bool value) {
   if (value) {
-    _flags |= _on_stack;
+    int old_flags = *const_cast<volatile int *>(&_flags);
+    while ((old_flags & _on_stack) == 0) {
+      int new_flags = old_flags | _on_stack;
+      int result = Atomic::cmpxchg(new_flags, &_flags, old_flags);
+
+      if (result == old_flags) {
+        // Succeeded.
+        MetadataOnStackMark::record(this, Thread::current());
+        return;
+      }
+      old_flags = result;
+    }
   } else {
+    // Clearing is done single-threadedly.
     _flags &= ~_on_stack;
   }
-  if (value) MetadataOnStackMark::record(this);
 }
 
 // JSR 292 support for patching constant pool oops after the class is linked and
 // the oop array for resolved references are created.
 // We can't do this during classfile parsing, which is how the other indexes are