fix: get rid of data race in encoder and fix concurrent map access

Fixes: #3377, #3380

Fixed the data race in the encoder documentation examples by using `sync.Once`.
We only need to generate them once anyways and then it's not a big deal
that we are using the same pointers everywhere as they're pretty much
constant.

As of `system.go`, looks like we actually have concurrent operations for
partitions unmount so I just added a mutex there.

Signed-off-by: Artem Chernyshev <artem.0xD2@gmail.com>

internal/pkg/mount/system.go

@@ -7,6 +7,7 @@ package mount
 import (
 	"fmt"
 	"os"
+	"sync"
 
 	"github.com/talos-systems/go-blockdevice/blockdevice"
 	"github.com/talos-systems/go-blockdevice/blockdevice/filesystem"
@@ -20,7 +21,10 @@ import (
 	"github.com/talos-systems/talos/pkg/machinery/constants"
 )
 
-var mountpoints = map[string]*Point{}
+var (
+	mountpoints      = map[string]*Point{}
+	mountpointsMutex sync.RWMutex
+)
 
 // SystemMountPointsForDevice returns the mountpoints required to boot the system.
 // This function is called exclusively during installations ( both image
@@ -195,21 +199,32 @@ func SystemPartitionMount(r runtime.Runtime, label string, opts ...Option) (err
 		return err
 	}
 
+	mountpointsMutex.Lock()
+	defer mountpointsMutex.Unlock()
+
 	mountpoints[label] = mountpoint
 
 	return nil
 }
 
 // SystemPartitionUnmount unmounts a system partition by the label.
 func SystemPartitionUnmount(r runtime.Runtime, label string) (err error) {
-	if mountpoint, ok := mountpoints[label]; ok {
-		err = mountpoint.Unmount()
-		if err != nil {
-			return err
-		}
+	mountpointsMutex.RLock()
+	mountpoint, ok := mountpoints[label]
+	mountpointsMutex.RUnlock()
 
-		delete(mountpoints, label)
+	if !ok {
+		return nil
 	}
 
+	err = mountpoint.Unmount()
+	if err != nil {
+		return err
+	}
+
+	mountpointsMutex.Lock()
+	delete(mountpoints, label)
+	mountpointsMutex.Unlock()
+
 	return nil
 }

pkg/machinery/config/encoder/documentation.go

@@ -8,6 +8,7 @@ import (
 	"reflect"
 	"regexp"
 	"strings"
+	"sync"
 
 	yaml "gopkg.in/yaml.v3"
 )
@@ -51,7 +52,7 @@ func (d *Doc) AddExample(name string, value interface{}) {
 
 	d.Examples = append(d.Examples, &Example{
 		Name:  name,
-		Value: value,
+		value: value,
 	})
 }
 
@@ -74,8 +75,43 @@ func (d *Doc) Describe(field string, short bool) string {
 
 // Example represents one example snippet for a type.
 type Example struct {
-	Name  string
-	Value interface{}
+	populate sync.Once
+	Name     string
+
+	valueMutex sync.RWMutex
+	value      interface{}
+}
+
+// Populate populates example value.
+func (e *Example) Populate(index int) {
+	e.populate.Do(func() {
+		if reflect.TypeOf(e.value).Kind() != reflect.Ptr {
+			return
+		}
+
+		v := reflect.ValueOf(e.value).Elem()
+
+		defaultValue := getExample(v, getDoc(e.value), index)
+
+		e.valueMutex.Lock()
+		defer e.valueMutex.Unlock()
+
+		if defaultValue != nil {
+			v.Set(defaultValue.Convert(v.Type()))
+		}
+
+		populateNestedExamples(v, index)
+	})
+}
+
+// GetValue returns example value.
+func (e *Example) GetValue() interface{} {
+	e.valueMutex.RLock()
+	defer func() {
+		e.valueMutex.RUnlock()
+	}()
+
+	return e.value
 }
 
 // Field gets field from the list of fields.
@@ -168,7 +204,7 @@ func renderExample(key string, doc *Doc) string {
 	examples := []string{}
 
 	for i, e := range doc.Examples {
-		v := reflect.ValueOf(e.Value)
+		v := reflect.ValueOf(e.GetValue())
 
 		if !isSet(v) {
 			continue
@@ -179,7 +215,8 @@ func renderExample(key string, doc *Doc) string {
 		}
 
 		defaultValue := v.Interface()
-		populateExamples(defaultValue, i)
+
+		e.Populate(i)
 
 		node, err := toYamlNode(defaultValue)
 		if err != nil {
@@ -229,61 +266,56 @@ func renderExample(key string, doc *Doc) string {
 	return strings.Join(examples, "")
 }
 
-func readExample(v reflect.Value, doc *Doc, index int) {
+func getExample(v reflect.Value, doc *Doc, index int) *reflect.Value {
 	if doc == nil || len(doc.Examples) == 0 {
-		return
+		return nil
 	}
 
 	numExamples := len(doc.Examples)
 	if index >= numExamples {
 		index = numExamples - 1
 	}
 
-	defaultValue := reflect.ValueOf(doc.Examples[index].Value)
+	defaultValue := reflect.ValueOf(doc.Examples[index].GetValue())
 	if isSet(defaultValue) {
 		if v.Kind() != reflect.Ptr && defaultValue.Kind() == reflect.Ptr {
 			defaultValue = defaultValue.Elem()
 		}
-
-		v.Set(defaultValue.Convert(v.Type()))
 	}
+
+	return &defaultValue
 }
 
 //nolint:gocyclo
-func populateExamples(in interface{}, index int) {
-	doc := getDoc(in)
-
-	if reflect.TypeOf(in).Kind() != reflect.Ptr {
-		return
-	}
-
-	v := reflect.ValueOf(in).Elem()
-
-	readExample(v, doc, index)
-
+func populateNestedExamples(v reflect.Value, index int) {
 	//nolint:exhaustive
 	switch v.Kind() {
 	case reflect.Struct:
+		doc := getDoc(v.Interface())
+
 		for i := 0; i < v.NumField(); i++ {
 			field := v.Field(i)
 			if !field.CanInterface() {
 				continue
 			}
 
 			if doc != nil && i < len(doc.Fields) {
-				readExample(field, doc.Field(i), index)
+				defaultValue := getExample(field, doc.Field(i), index)
+
+				if defaultValue != nil {
+					field.Set(defaultValue.Convert(field.Type()))
+				}
 			}
 
-			value := field.Interface()
-			populateExamples(value, index)
+			populateNestedExamples(field, index)
 		}
 	case reflect.Map:
 		for _, key := range v.MapKeys() {
-			populateExamples(v.MapIndex(key), index)
+			populateNestedExamples(v.MapIndex(key), index)
 		}
 	case reflect.Slice:
 		for i := 0; i < v.Len(); i++ {
-			populateExamples(v.Index(i), index)
+			populateNestedExamples(v.Index(i), index)
 		}
 	}
 }

pkg/machinery/config/encoder/encoder_test.go

@@ -5,6 +5,7 @@
 package encoder_test
 
 import (
+	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/suite"
@@ -94,40 +95,25 @@ func init() {
 	mixinDoc.Fields = make([]encoder.Doc, 1)
 	mixinDoc.Fields[0].Comments[encoder.LineComment] = "was inlined"
 
-	machineDoc.Examples = []*encoder.Example{
-		{
-			Name: "uncomment me",
-			Value: &Machine{
-				State: 100,
-			},
-		},
-		{
-			Name: "second example",
-			Value: &Machine{
-				State: -1,
-			},
-		},
-	}
+	machineDoc.AddExample("uncomment me", &Machine{
+		State: 100,
+	})
+	machineDoc.AddExample("second example", &Machine{
+		State: -1,
+	})
+
 	machineDoc.Fields = make([]encoder.Doc, 2)
-	machineDoc.Fields[1].Examples = []*encoder.Example{
-		{
-			Name: "",
-			Value: &MachineConfig{
-				Version: "0.0.2",
-			},
-		},
-	}
+	machineDoc.Fields[1].AddExample("", &MachineConfig{
+		Version: "0.0.2",
+	})
 
 	machineConfigDoc.Fields = make([]encoder.Doc, 2)
 	machineConfigDoc.Fields[0].Comments[encoder.HeadComment] = "this is some version"
-	machineConfigDoc.Fields[1].Examples = []*encoder.Example{
-		{
-			Name: "",
-			Value: []string{
-				"reboot", "upgrade",
-			},
+	machineConfigDoc.Fields[1].AddExample("",
+		[]string{
+			"reboot", "upgrade",
 		},
-	}
+	)
 }
 
 func (c Config) Doc() *encoder.Doc {
@@ -329,6 +315,23 @@ mixed_in: a # was inlined
     #     capabilities:
     #         - reboot
     #         - upgrade
+`,
+			incompatible: true,
+		},
+		{
+			name: "populate map element's examples",
+			value: map[string][]*MachineConfig{
+				"first": {
+					{},
+				},
+			},
+			expectedYAML: `first:
+    - # this is some version
+      version: ""
+      
+      # capabilities:
+      #     - reboot
+      #     - upgrade
 `,
 			incompatible: true,
 		},
@@ -361,6 +364,26 @@ mixed_in: a # was inlined
 	}
 }
 
+func (suite *EncoderSuite) TestConcurrent() {
+	value := &Machine{}
+
+	var wg sync.WaitGroup
+
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+
+		go func() {
+			defer wg.Done()
+
+			encoder := encoder.NewEncoder(value)
+			_, err := encoder.Encode()
+			suite.Assert().NoError(err)
+		}()
+	}
+
+	wg.Wait()
+}
+
 func decodeToMap(data []byte) (map[interface{}]interface{}, error) {
 	raw := map[interface{}]interface{}{}
 	err := yaml.Unmarshal(data, &raw)

pkg/machinery/config/encoder/markdown.go

@@ -21,7 +21,7 @@ var markdownTemplate = `
 Examples:
 
 {{ range $example := .Examples }}
-{{ yaml $example.Value $.Name }}
+{{ yaml $example.GetValue $.Name }}
 {{ end }}
 {{ end }}
 
@@ -43,7 +43,7 @@ Appears in:
 {{ if $struct.Examples -}}
 
 {{ range $example := $struct.Examples }}
-{{ yaml $example.Value "" }}
+{{ yaml $example.GetValue "" }}
 {{- end -}}
 {{ end }}