RFR: 8262316: Reducing locks in RSA Blinding [v2]

[Anthony Scarpino]

On Sat, 3 Apr 2021 05:40:11 GMT, djelinski <github.com+30433125+djelinski at openjdk.org> wrote:

>> If you synchronize `putIfAbsent` but not `get` you'll still get the possible infinite loop described in the SO post.
>
> Expunging entries is synchronized over an internal data structure, so if you synchronize puts only, nothing prevents expunge (called from get) from running in parallel with put.
> The original code performed big integer exponentiation inside a synchronized block, your code doesn't. I expect substantial performance gains even with synchronization around hash map access, this is why I asked about performance.

I finally see that get() is affected by the locking.  Expunge seems to not lock the able which could cause multiple threads get ops to corrupt the map.  I'll put a ReentrantLock around the put & get.  I prefer to not use synchronized() blocks as ReentrantLock maybe better after Project Loom

Sure, the performance was largely affected by the math ops in the old code.  I wanted to eliminate as much of the performance decelerators as possible

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PR: https://git.openjdk.java.net/jdk/pull/3296