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

[Andrew Haley]

On 09/09/2015 02:55 PM, David M. Lloyd wrote:
> On 09/09/2015 08:17 AM, Andrew Haley wrote:
>> On 09/09/2015 02:13 PM, David M. Lloyd wrote:
>>> How would you hook into the safepoint to perform the unmapping?  You'd
>>> have to wait for all threads to arrive at safepoints, wouldn't you?
>>
>> Yes.  That happens in the VM already, e.g. when we need to revoke the
>> bias of a lock.  It's a well-established mechanism.
> 
> Could you extend the technique to other native resources as well?

Yes, but of course there will be some back-pressure from HotSpot
developers: it requires changes to the VM, and you have to be
extremely careful not to cause a deadlock.

Andrew.