question: private boolean tryRelease ( long c , WorkQueue v , long inc ) { int sp = ( int ) c , ns = sp & ~ UNSIGNALLED ; if ( v != null ) { int vs = v . scanState ; long nc = ( v . stackPred & SP_MASK ) | ( UC_MASK & ( c + inc ) ) ; if ( sp == vs && U . compareAndSwapLong ( this , CTL , c , nc ) ) { v . scanState = ns ; LockSupport . unpark ( v . parker ) ; return true ; } } return false ; }
target:  Signals and releases worker v if it is top of idle worker stack.  This performs a one-shot version of signalWork only if there is (apparently) at least one idle worker.