func VirtualizationWithContext()

in patches/gopsutil/v3/internal/common/common_linux.go [118:258]
123 lines of code
38 McCabe index (conditional complexity)

func VirtualizationWithContext(ctx context.Context) (string, string, error) {
	var system, role string

	// if cached already, return from cache
	cachedVirtMutex.RLock() // unlock won't be deferred so concurrent reads don't wait for long
	if cachedVirtMap != nil {
		cachedSystem, cachedRole := cachedVirtMap["system"], cachedVirtMap["role"]
		cachedVirtMutex.RUnlock()
		return cachedSystem, cachedRole, nil
	}
	cachedVirtMutex.RUnlock()

	filename := HostProc("xen")
	if PathExists(filename) {
		system = "xen"
		role = "guest" // assume guest

		if PathExists(filepath.Join(filename, "capabilities")) {
			contents, err := ReadLines(filepath.Join(filename, "capabilities"))
			if err == nil {
				if StringsContains(contents, "control_d") {
					role = "host"
				}
			}
		}
	}

	filename = HostProc("modules")
	if PathExists(filename) {
		contents, err := ReadLines(filename)
		if err == nil {
			if StringsContains(contents, "kvm") {
				system = "kvm"
				role = "host"
			} else if StringsContains(contents, "vboxdrv") {
				system = "vbox"
				role = "host"
			} else if StringsContains(contents, "vboxguest") {
				system = "vbox"
				role = "guest"
			} else if StringsContains(contents, "vmware") {
				system = "vmware"
				role = "guest"
			}
		}
	}

	filename = HostProc("cpuinfo")
	if PathExists(filename) {
		contents, err := ReadLines(filename)
		if err == nil {
			if StringsContains(contents, "QEMU Virtual CPU") ||
				StringsContains(contents, "Common KVM processor") ||
				StringsContains(contents, "Common 32-bit KVM processor") {
				system = "kvm"
				role = "guest"
			}
		}
	}

	filename = HostProc("bus/pci/devices")
	if PathExists(filename) {
		contents, err := ReadLines(filename)
		if err == nil {
			if StringsContains(contents, "virtio-pci") {
				role = "guest"
			}
		}
	}

	filename = HostProc()
	if PathExists(filepath.Join(filename, "bc", "0")) {
		system = "openvz"
		role = "host"
	} else if PathExists(filepath.Join(filename, "vz")) {
		system = "openvz"
		role = "guest"
	}

	// not use dmidecode because it requires root
	if PathExists(filepath.Join(filename, "self", "status")) {
		contents, err := ReadLines(filepath.Join(filename, "self", "status"))
		if err == nil {
			if StringsContains(contents, "s_context:") ||
				StringsContains(contents, "VxID:") {
				system = "linux-vserver"
			}
			// TODO: guest or host
		}
	}

	if PathExists(filepath.Join(filename, "1", "environ")) {
		contents, err := ReadFile(filepath.Join(filename, "1", "environ"))

		if err == nil {
			if strings.Contains(contents, "container=lxc") {
				system = "lxc"
				role = "guest"
			}
		}
	}

	if PathExists(filepath.Join(filename, "self", "cgroup")) {
		contents, err := ReadLines(filepath.Join(filename, "self", "cgroup"))
		if err == nil {
			if StringsContains(contents, "lxc") {
				system = "lxc"
				role = "guest"
			} else if StringsContains(contents, "docker") {
				system = "docker"
				role = "guest"
			} else if StringsContains(contents, "machine-rkt") {
				system = "rkt"
				role = "guest"
			} else if PathExists("/usr/bin/lxc-version") {
				system = "lxc"
				role = "host"
			}
		}
	}

	if PathExists(HostEtc("os-release")) {
		p, _, err := GetOSRelease()
		if err == nil && p == "coreos" {
			system = "rkt" // Is it true?
			role = "host"
		}
	}

	// before returning for the first time, cache the system and role
	cachedVirtOnce.Do(func() {
		cachedVirtMutex.Lock()
		defer cachedVirtMutex.Unlock()
		cachedVirtMap = map[string]string{
			"system": system,
			"role":   role,
		}
	})

	return system, role, nil
}