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

*** 1815,1829 ****
  #undef DBG
  
  
  void ConstantPool::set_on_stack(const bool value) {
    if (value) {
!     _flags |= _on_stack;
    } else {
      _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
--- 1815,1840 ----
  #undef DBG
  
  
  void ConstantPool::set_on_stack(const bool value) {
    if (value) {
!     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;
    }
  }
  
  // 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