if atomic.CasRel(&pp.runqhead, h, h+1) { // cas-release, commits consume
			return gp, false
		}
	}
}

// runqdrain drains the local runnable queue of pp and returns all goroutines in it.
// Executed only by the owner P.
func runqdrain(pp *p) (drainQ gQueue, n uint32) {
	oldNext := pp.runnext
	if oldNext != 0 && pp.runnext.cas(oldNext, 0) {
		drainQ.pushBack(oldNext.ptr())
		n++
	}