golang调度学习-调度流程 (四) mstart

不管是rt0_go还是go语法(如果在有idle的情况下)最终都会调用mstart

mstart

// mstart is the entry-point for new Ms.
//
// This must not split the stack because we may not even have stack
// bounds set up yet.
//
// May run during STW (because it doesn't have a P yet), so write
// barriers are not allowed.
//
//go:nosplit
//go:nowritebarrierrec
func mstart() {
    _g_ := getg()

    osStack := _g_.stack.lo == 0
    if osStack {
        // Initialize stack bounds from system stack.
        // Cgo may have left stack size in stack.hi.
        // minit may update the stack bounds.
        //
        // Note: these bounds may not be very accurate.
        // We set hi to &size, but there are things above
        // it. The 1024 is supposed to compensate this,
        // but is somewhat arbitrary.
        size := _g_.stack.hi
        if size == 0 {
            size = 8192 * sys.StackGuardMultiplier
        }
        _g_.stack.hi = uintptr(noescape(unsafe.Pointer(&size)))
        _g_.stack.lo = _g_.stack.hi - size + 1024
    }
    // Initialize stack guard so that we can start calling regular
    // Go code.
    _g_.stackguard0 = _g_.stack.lo + _StackGuard
    // This is the g0, so we can also call go:systemstack
    // functions, which check stackguard1.
    _g_.stackguard1 = _g_.stackguard0
    mstart1()

    // Exit this thread.
    if mStackIsSystemAllocated() {
        // Windows, Solaris, illumos, Darwin, AIX and Plan 9 always system-allocate
        // the stack, but put it in _g_.stack before mstart,
        // so the logic above hasn't set osStack yet.
        osStack = true
    }
    mexit(osStack)
}