mp := acquirem()
	if !lockheld {
		lock(&sched.lock)
	}
	if pp == nil {
		if spinning {
			// TODO(prattmic): All remaining calls to this function
			// with _p_ == nil could be cleaned up to find a P
			// before calling startm.
			throw("startm: P required for spinning=true")
		}
		pp, _ = pidleget(0)
		if pp == nil {
			if !lockheld {
				unlock(&sched.lock)
			}