@@ -2,6 +2,7 @@ package layer // import "github.com/docker/docker/layer"

 import (

 	"io"

+	"sync"

 	"github.com/docker/docker/pkg/archive"

 	"github.com/docker/docker/pkg/containerfs"

@@ -15,6 +16,7 @@ type mountedLayer struct {

 	path       string

 	layerStore *layerStore

+	sync.Mutex

 	references map[RWLayer]*referencedRWLayer

 }

@@ -62,16 +64,24 @@ func (ml *mountedLayer) getReference() RWLayer {

 	ref := &referencedRWLayer{

 		mountedLayer: ml,

 	}

+	ml.Lock()

 	ml.references[ref] = ref

+	ml.Unlock()

 	return ref

 }

 func (ml *mountedLayer) hasReferences() bool {

-	return len(ml.references) > 0

+	ml.Lock()

+	ret := len(ml.references) > 0

+	ml.Unlock()

+

+	return ret

 }

 func (ml *mountedLayer) deleteReference(ref RWLayer) error {

+	ml.Lock()

+	defer ml.Unlock()

 	if _, ok := ml.references[ref]; !ok {

 		return ErrLayerNotRetained

 	}

@@ -81,7 +91,9 @@ func (ml *mountedLayer) deleteReference(ref RWLayer) error {

 func (ml *mountedLayer) retakeReference(r RWLayer) {

 	if ref, ok := r.(*referencedRWLayer); ok {

+		ml.Lock()

 		ml.references[ref] = ref

+		ml.Unlock()

 	}

 }