1 files changed, 5 insertions, 27 deletions
diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index 68512d0225..e7e7c4b7ef 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -21,7 +21,6 @@ import (
 	"strconv"
 	"strings"
 	"sync"
-	"sync/atomic"
 	"unicode"
 	"unicode/utf8"
 )
@@ -1258,34 +1257,13 @@ func dominantField(fields []field) (field, bool) {
 	return fields[0], true
 }
 
-var fieldCache struct {
-	value atomic.Value // map[reflect.Type][]field
-	mu    sync.Mutex   // used only by writers
-}
+var fieldCache sync.Map // map[reflect.Type][]field
 
 // cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
 func cachedTypeFields(t reflect.Type) []field {
-	m, _ := fieldCache.value.Load().(map[reflect.Type][]field)
-	f := m[t]
-	if f != nil {
-		return f
-	}
-
-	// Compute fields without lock.
-	// Might duplicate effort but won't hold other computations back.
-	f = typeFields(t)
-	if f == nil {
-		f = []field{}
+	if f, ok := fieldCache.Load(t); ok {
+		return f.([]field)
 	}
-
-	fieldCache.mu.Lock()
-	m, _ = fieldCache.value.Load().(map[reflect.Type][]field)
-	newM := make(map[reflect.Type][]field, len(m)+1)
-	for k, v := range m {
-		newM[k] = v
-	}
-	newM[t] = f
-	fieldCache.value.Store(newM)
-	fieldCache.mu.Unlock()
-	return f
+	f, _ := fieldCache.LoadOrStore(t, typeFields(t))
+	return f.([]field)
 }