Summary
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Method `LockSupport.setCurrentBlocker` was added as part of JDK-8229442 mainly to allow implementations to maintain compatibility with tools and
utilities reporting `LockSupport.getBlocker` when threads are parked.

Problem
-------
The primary rationale for this method is to allow people to improve
compatibility with previous implementations that includes calls to `LockSupport.park`,  with respect to tools expecting a particular type of blocker object to be reported in stack traces etc. 

Solution
--------

`LockSupport.setCurrentBlocker` allows a given blocker to be set instead of per-park arguments for upcoming calls to park that may be performed in some other object.


Specification
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    /**
     * Sets the object to be returned by invocations of {@link
     * #getBlocker getBlocker} for the current thread. This method may
     * be used before invoking the no-argument version of {@link
     * LockSupport#park() park()} from non-public objects, allowing
     * more helpful diagnostics, or retaining compatibility with
     * previous implementations of blocking methods.  Previous values
     * of the blocker are not automatically restored after blocking.
     * To obtain the effects of {@code park(b}}, use {@code
     * setCurrentBlocker(b); park(); setCurrentBlocker(null);}
     *
     * @param blocker the blocker object
     * @since 14
     */
    public static void setCurrentBlocker(Object blocker) {
        U.putObjectOpaque(Thread.currentThread(), PARKBLOCKER, blocker);
    }