1) indeed there are a couple of barriers that could be optimized<p>2) in addition to what Phil already said (which is that there&#x27;s no priority inversion for Safari&#x2F;WebKit to have as all threads taking these locks have the same priority to boot), the private lock you&#x27;re talking about, named the handoff lock, has terrible unlock patterns, and is why it performs so poorly when WTF::Lock benched it.