question: private long tryIncReaderOverflow ( long s ) { if ( ( s & ABITS ) == RFULL ) { if ( U . compareAndSwapLong ( this , STATE , s , s | RBITS ) ) { ++ readerOverflow ; U . putLongVolatile ( this , STATE , s ) ; return s ; } } else if ( ( nextSecondarySeed ( ) & OVERFLOW_YIELD_RATE ) == 0 ) Thread . yield ( ) ; return 0L ; }
target:  Tries to increment readerOverflow by first setting state access bits value to RBITS, indicating hold of spinlock, then updating, then releasing.