请教一个问题

在学习GMP的过程中,runtime/proc.go这个源码里出现了之前没有学习过的源码

top:
    _p_ := _g_.m.p.ptr()
    if sched.gcwaiting != 0 {
        gcstopm()
        goto top
    }
    if _p_.runSafePointFn != 0 {
        runSafePointFn()
    }

    now, pollUntil, _ := checkTimers(_p_, 0)

    if fingwait && fingwake {
        if gp := wakefing(); gp != nil {
            ready(gp, 0, true)
        }
    }
    if *cgo_yield != nil {
        asmcgocall(*cgo_yield, nil)
    }
......
stop:
    // We have nothing to do. If we're in the GC mark phase, can
    // safely scan and blacken objects, and have work to do, run
    // idle-time marking rather than give up the P.
    if gcBlackenEnabled != 0 && gcMarkWorkAvailable(_p_) {
        node := (*gcBgMarkWorkerNode)(gcBgMarkWorkerPool.pop())
        if node != nil {
            _p_.gcMarkWorkerMode = gcMarkWorkerIdleMode
            gp := node.gp.ptr()
            casgstatus(gp, _Gwaiting, _Grunnable)
            if trace.enabled {
                traceGoUnpark(gp, 0)
            }
            return gp, false
        }
    }
......

这里想请教一下,top和stop的用法以及触发goto的时候是从top的下一行开始执行吗?