@@ -133,11 +133,12 @@ func getVolumeDriver(name string) (volume.Driver, error) {

 // Create tries to find an existing volume with the given name or create a new one from the passed in driver

 func (s *volumeStore) Create(name, driverName string, opts map[string]string) (volume.Volume, error) {

 	s.mu.Lock()

-	defer s.mu.Unlock()

-

 	if vc, exists := s.vols[name]; exists {

-		return vc.Volume, nil

+		v := vc.Volume

+		s.mu.Unlock()

+		return v, nil

 	}

+	s.mu.Unlock()

 	vd, err := getVolumeDriver(driverName)

 	if err != nil {

@@ -149,7 +150,10 @@ func (s *volumeStore) Create(name, driverName string, opts map[string]string) (v

 		return nil, err

 	}

+	s.mu.Lock()

 	s.vols[v.Name()] = &volumeCounter{v, 0}

+	s.mu.Unlock()

+

 	return v, nil

 }

@@ -9,8 +9,10 @@ import (

 	"net/http"

 	"net/http/httptest"

 	"os"

+	"os/exec"

 	"path/filepath"

 	"strings"

+	"time"

 	"github.com/go-check/check"

 )

@@ -271,3 +273,40 @@ func (s *DockerExternalVolumeSuite) TestStartExternalNamedVolumeDriverCheckBindL

 	c.Assert(s.ec.mounts, check.Equals, 1)

 	c.Assert(s.ec.unmounts, check.Equals, 1)

 }

+

+// Make sure a request to use a down driver doesn't block other requests

+func (s *DockerExternalVolumeSuite) TestStartExternalVolumeDriverLookupNotBlocked(c *check.C) {

+	specPath := "/etc/docker/plugins/down-driver.spec"

+	err := ioutil.WriteFile("/etc/docker/plugins/down-driver.spec", []byte("tcp://127.0.0.7:9999"), 0644)

+	c.Assert(err, check.IsNil)

+	defer os.RemoveAll(specPath)

+

+	chCmd1 := make(chan struct{})

+	chCmd2 := make(chan error)

+	cmd1 := exec.Command(dockerBinary, "volume", "create", "-d", "down-driver")

+	cmd2 := exec.Command(dockerBinary, "volume", "create")

+

+	c.Assert(cmd1.Start(), check.IsNil)

+	defer cmd1.Process.Kill()

+	time.Sleep(100 * time.Millisecond) // ensure API has been called

+	c.Assert(cmd2.Start(), check.IsNil)

+

+	go func() {

+		cmd1.Wait()

+		close(chCmd1)

+	}()

+	go func() {

+		chCmd2 <- cmd2.Wait()

+	}()

+

+	select {

+	case <-chCmd1:

+		cmd2.Process.Kill()

+		c.Fatalf("volume create with down driver finished unexpectedly")

+	case err := <-chCmd2:

+		c.Assert(err, check.IsNil, check.Commentf("error creating volume"))

+	case <-time.After(5 * time.Second):

+		c.Fatal("volume creates are blocked by previous create requests when previous driver is down")

+		cmd2.Process.Kill()

+	}

+}