Question

标准库 runtime 里与调度有关的几个函数。

Gosched

与 gopark 的区别在于：会被放回队列，无需 goready 唤醒。

// proc.go

// Gosched yields the processor, allowing other goroutines to run. It does not
// suspend the current goroutine, so execution resumes automatically.

func Gosched() {
    // mcall 会保存当前 G.sched，并将 G 做为 gosched_m 调用参数。
    mcall(gosched_m)
}

// Gosched continuation on g0.

func gosched_m(gp *g) {
    goschedImpl(gp)
}

func goschedImpl(gp *g) {
    
    // 切换状态，并解除 gp 和 MP 的关联。
    casgstatus(gp, _Grunning, _Grunnable)
    dropg()
    
    // 将 gp 放入全局队列，等待下次被调度执行。
    globrunqput(gp)
    
    // 当前 MP 调度其他任务。
    schedule()
}

Goexit

调用 goexit1，将当前 G 标记为 dead 状态，放回复用列表。

解除和 M 的关联，让其重新进入调度循环。

这意味着立即终止，不会再回到 G 执行，不理会调用堆栈。

在 main goroutine 里调用 Goexit，它会等待其他 goroutine 结束后才会崩溃。

// panic.go

// Goexit terminates the goroutine that calls it. No other goroutine is affected.
//
// Goexit runs all deferred calls before terminating the goroutine. Because Goexit
// is not a panic, any recover calls in those deferred functions will return nil.
//
// Calling Goexit from the main goroutine terminates that goroutine
// without func main returning. Since func main has not returned,
// the program continues execution of other goroutines.
// If all other goroutines exit, the program crashes.

func Goexit() {
    for {
        ...defer...
    }
    
    goexit1()
}