// newSigstack, so that it can be undone in unminit.
func minitSignalStack() {
	mp := getg().m
	var st stackt
	sigaltstack(nil, &st)
	if st.ss_flags&_SS_DISABLE != 0 || !iscgo {
		signalstack(&mp.gsignal.stack)
		mp.newSigstack = true
	} else {
		setGsignalStack(&st, &mp.goSigStack)
		mp.newSigstack = false
	}
}

	locks         int32
	dying         int32
	profilehz     int32
	spinning      bool // m is out of work and is actively looking for work
	blocked       bool // m is blocked on a note
	newSigstack   bool // minit on C thread called sigaltstack
	printlock     int8
	incgo         bool          // m is executing a cgo call
	isextra       bool          // m is an extra m