RFR: 8277954: Replace use of monitors with explicit locks in the JDK LDAP provider implementation

[Daniel Fuchs]

On Thu, 31 Aug 2023 22:48:30 GMT, Aleksei Efimov <aefimov at openjdk.org> wrote:

> The change proposed in this PR improves the behavior of the JDK JNDI/LDAP provider when running in a virtual thread. Currently, when an LDAP operation is performed from a virtual thread context a pinned carrier thread is detected:
> 
>      Thread[#29,ForkJoinPool-1-worker-1,5,CarrierThreads]
>         java.naming/com.sun.jndi.ldap.Connection.read reply(Connection.java:444) <== monitors:1
>         java.naming/com.sun.jndi.ldap.LdapClient.ldapBind(LdapClient.java:369) <== monitors:1
>         java.naming/com.sun.jndi.ldap.LdapClient.authenticate(LdapClient.java:196) <== monitors:1
>         java.naming/com.sun.jndi.ldap.LdapCtx.connect(LdapCtx.java:2896) <== monitors:1
> 
> To fix that monitor usages are replaced with `j.u.c` locks. All synchronized blocks/methods have been replaced with locks even if it is only guarding memory access - the motivation behind such a decision was to avoid an analysis of scenarios where a mix of monitors and `j.u.c` locks is used.
> 
> There are three types of mechanical changes done in this PR:
> 
> 1. Classes with `synchronized` blocks or `synchronized` methods have been updated to include a new `ReentrantLock` field. These new fields are used to replace `synchronized` blocks/methods.
> 1. classes that use notify/wait on object monitor have been updated to use `ReentrantLock.Condition`s signal/await.
> 1. if one class `synchronized` on an instance of another class - the `ReentrantLock` added in item (1) was made a package-protected to give access to another class.
> 
> With the proposed changes pinned carrier threads are no longer detected during execution of LDAP operations. 
> 
> Testing: `jdk-tier1` to `jdk-tier3`, other `jndi/ldap` regression and JCK naming tests show no failures.

Look reasonable to me. If tier2 and all jndi tests are still passing, I'm good with it.

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Marked as reviewed by dfuchs (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15526#pullrequestreview-1617680805