Suggested fix for JDK-4724038 (Add unmap method to MappedByteBuffer)

[Andrew Haley]

On 09/08/2015 02:05 PM, Andrew Haley wrote:
> I don't think you'd actually need to unmap anything until a safepoint.
> I don't think that the speed of unmapping is critical as long as it
> happens "soon".

Although given the desire to do

  buffer.unmap();
  file.delete();

that belief may be misplaced.  We could just block for a safepoint;
we already do that in other cases, and there's no guarantee about how
long unmap() would take to execute.

Andrew.