var runtime.extraM

4 uses

	runtime (current package)
		proc.go#L2731: 	extraM atomic.Uintptr
		proc.go#L2753: 		old := extraM.Load()
		proc.go#L2769: 		if extraM.CompareAndSwap(old, locked) {
		proc.go#L2780: 	extraM.Store(uintptr(unsafe.Pointer(mp)))

The pages are generated with Golds v0.7.6. (GOOS=linux GOARCH=amd64)