[9] RFR (S) File leak in MemNotifyThread::start() in hotspot.src.os.linux.vm.os_linux.cpp

[Chris Plummer]

Hi,

Please review this change to fix a leaking fd.

Summary: Fixed by removing all code related to LowMemoryProtection, 
which removed offending code.

Webrev: http://cr.openjdk.java.net/~cjplummer/8043770/webrev.00/
Bug: https://bugs.openjdk.java.net/browse/JDK-8043770

Tested with jprt "-testset hotspot"

Details: The offending code is there to support the 
-XX:+LowMemoryProtection flag, which relies on linux kernel support for 
/dev/mem_notify. Although the leak was easy to fix, I ran into an issue 
testing it. Apparently we have no devices that support /dev/mem_notify, 
and SQE is not testing this feature. It also turns out that in general 
/dev/mem_notify support has not been adopted, so LowMemoryProtection is 
of limited or no value, and in fact is a liability since we are not 
testing it. The decision was made to remove the support instead, thus 
also fixing the fd leak. This only affects builds with JAVASE_EMBEDDED 
enabled, so will not impact any JDK release.

thanks,

Chris