var runtime.extraM

4 uses

	runtime (current package)
		proc.go#L2254: 	extraM atomic.Uintptr
		proc.go#L2276: 		old := extraM.Load()
		proc.go#L2292: 		if extraM.CompareAndSwap(old, locked) {
		proc.go#L2303: 	extraM.Store(uintptr(unsafe.Pointer(mp)))