[jdk9] RFR: 8080273: JCA Signature provider service loading bottlenecks

[Ivan Gerasimov]

Hello!

It has been observed that under some circumstances a scalability 
bottleneck may be observed, when accessing the internal 
BlindingParameters structure in the sun.security.rsa.RSACore class.

It is proposed to slightly reorganize the code around, to reduce the 
possible contention.

Would you please help review the proposal?

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8080273
WEBREV: http://cr.openjdk.java.net/~igerasim/8080273/00/webrev/

Three things are done here:
1) The instance of BlindingParameters is confined to the current thread, 
so no synchronization is necessary when creating the next 
BlindingRandomPair;
2) Extra instances of BlindingParameters, which are created due to 
concurency, aren't thrown away but reused;
3) Only perform { u = u.modPow(BIG_TWO, n);  v = v.modPow(BIG_TWO, n); } 
when needed, thus save the last unused calculation.

Comments, suggestions are very welcome!

With kind regards,
Ivan