type g struct {
	// 栈相关的两个字段
	stack       stack
	stackguard0 uintptr
	stackguard1 uintptr // offset known to liblink
	
	// defer 和 panic 
	_panic       *_panic // 最内侧的 panic 结构体
	_defer       *_defer // 最内侧的延迟函数结构体

	//
	m              *m
	sched          gobuf
	atomicstatus   uint32
	goid           int64

	// 抢占
	preempt       bool // 抢占信号
	preemptStop   bool // 抢占时将状态修改成 `_Gpreempted`
	preemptShrink bool // 在同步安全点收缩栈
}

type gobuf struct {
	sp   uintptr
	pc   uintptr
	g    guintptr
	ctxt unsafe.Pointer
	ret  sys.Uintreg
	lr   uintptr
	bp   uintptr // for GOEXPERIMENT=framepointer   ------------------------here
}

type m struct {
	g0      *g     // goroutine with scheduling stack
	morebuf gobuf  // gobuf arg to morestack
	divmod  uint32 // div/mod denominator for arm - known to liblink

	// Fields not known to debuggers.
	procid        uint64       // for debuggers, but offset not hard-coded
	gsignal       *g           // signal-handling g
	goSigStack    gsignalStack // Go-allocated signal handling stack
	sigmask       sigset       // storage for saved signal mask
	tls           [6]uintptr   // thread-local storage (for x86 extern register)
	mstartfn      func()
	curg          *g       // current running goroutine

	//...
}

var (
	allglen    uintptr
	allm       *m
	allp       []*p  // len(allp) == gomaxprocs; may change at safe points, otherwise immutable
	allpLock   mutex // Protects P-less reads of allp and all writes
	gomaxprocs int32
	ncpu       int32
	sched      schedt
    //...
)

type schedt struct {
    //...
	// Global runnable queue. 全局运行队列
	runq     gQueue
    runqsize int32
    //...
}

// A gQueue is a dequeue of Gs linked through g.schedlink. A G can only
// be on one gQueue or gList at a time.
type gQueue struct {
	head guintptr
	tail guintptr
}

// Put gp on the global runnable queue.
// Sched must be locked.
// May run during STW, so write barriers are not allowed.
//go:nowritebarrierrec
func globrunqput(gp *g) {
	sched.runq.pushBack(gp)
	sched.runqsize++
}

// pushBack adds gp to the tail of q.
func (q *gQueue) pushBack(gp *g) {
	gp.schedlink = 0
	if q.tail != 0 {
		q.tail.ptr().schedlink.set(gp)
	} else {
		q.head.set(gp)
	}
	q.tail.set(gp)
}

type p struct{
	//...

	runqhead uint32
	runqtail uint32
	runq     [256]guintptr
	// runnext, if non-nil, is a runnable G that was ready'd by
	// the current G and should be run next instead of what's in
	// runq if there's time remaining in the running G's time
	// slice. It will inherit the time left in the current time
	// slice. If a set of goroutines is locked in a
	// communicate-and-wait pattern, this schedules that set as a
	// unit and eliminates the (potentially large) scheduling
	// latency that otherwise arises from adding the ready'd
	// goroutines to the end of the run queue.
	runnext guintptr

	//...
}

type p struct{
	//...

	runqhead uint32
	runqtail uint32
	runq     [256]guintptr
	// runnext, if non-nil, is a runnable G that was ready'd by
	// the current G and should be run next instead of what's in
	// runq if there's time remaining in the running G's time
	// slice. It will inherit the time left in the current time
	// slice. If a set of goroutines is locked in a
	// communicate-and-wait pattern, this schedules that set as a
	// unit and eliminates the (potentially large) scheduling
	// latency that otherwise arises from adding the ready'd
	// goroutines to the end of the run queue.
	runnext guintptr

	//...
}

/* 
----------------here:  这里是入队，把Goroutine放入本地运行队列
*/
	h := atomic.LoadAcq(&_p_.runqhead) // load-acquire, synchronize with consumers
	t := _p_.runqtail
	if t-h < uint32(len(_p_.runq)) {
		_p_.runq[t%uint32(len(_p_.runq))].set(gp)
		atomic.StoreRel(&_p_.runqtail, t+1) // store-release, makes the item available for consumption,runqhead不动,runqtail加一.
		return
	}

//----------------------------------------------------------------------------------------------------------

	for {
		h := atomic.LoadAcq(&_p_.runqhead) // load-acquire, synchronize with other consumers
		t := _p_.runqtail
		if t == h { // 如果头等于尾，证明是队列是空的
			return nil, false
		}
		gp := _p_.runq[h%uint32(len(_p_.runq))].ptr()
		if atomic.CasRel(&_p_.runqhead, h, h+1) { // cas-release, commits consume,runqhead加一,runqtail不动.
			return gp, false
		}
	}