RFR: 8252794: Creation of JNIMethodBlock should be done with a leaf lock

[Coleen Phillimore]

On Mon, 7 Sep 2020 12:16:17 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

> JVM TI uses handshakes and sometimes need jmethod ids.
> The CLD have an area where these ids are saved, which is created on first request for an id.
> 
> The creation of this area should be done with a leaf lock.
> In W.I.P. asynchronous handshake change-set we use a mutex instead of a semaphore for serializing the handshakes,
> we thus get into lock ranks asserts.
> 
> The CLD metaspace lock cannot be pushed down but we can use the same lock as for creating jmethod ids:
> JmethodIdCreation_lock. And push that down. (special-2 is picked to be compatible with W.I.P. asynchronous handshake
> change-set)
> The reason for CLD metaspace lock being used now is that we have one per CLD instead of one global one.
> 
> Testing passes: t1-3

Marked as reviewed by coleenp (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/53