@@ -55,17 +55,21 @@ func CmdStream(cmd *exec.Cmd) (io.Reader, error) {

 		return nil, err

 	}

 	pipeR, pipeW := io.Pipe()

+	errChan := make(chan []byte)

 	go func() {

-		_, err := io.Copy(pipeW, stdout)

-		if err != nil {

-			pipeW.CloseWithError(err)

-		}

 		errText, e := ioutil.ReadAll(stderr)

 		if e != nil {

 			errText = []byte("(...couldn't fetch stderr: " + e.Error() + ")")

 		}

+		errChan <- errText

+	}()

+	go func() {

+		_, err := io.Copy(pipeW, stdout)

+		if err != nil {

+			pipeW.CloseWithError(err)

+		}

+		errText := <-errChan

 		if err := cmd.Wait(); err != nil {

-			// FIXME: can this block if stderr outputs more than the size of StderrPipe()'s buffer?

 			pipeW.CloseWithError(errors.New(err.Error() + ": " + string(errText)))

 		} else {

 			pipeW.Close()

@@ -1,12 +1,26 @@

 package docker

 import (

+	"io"

 	"io/ioutil"

 	"os"

 	"os/exec"

 	"testing"

 )

+func TestCmdStreamLargeStderr(t *testing.T) {

+	// This test checks for deadlock; thus, the main failure mode of this test is deadlocking.

+	cmd := exec.Command("/bin/sh", "-c", "dd if=/dev/zero bs=1k count=1000 of=/dev/stderr; echo hello")

+	out, err := CmdStream(cmd)

+	if err != nil {

+		t.Fatalf("Failed to start command: " + err.Error())

+	}

+	_, err = io.Copy(ioutil.Discard, out)

+	if err != nil {

+		t.Fatalf("Command should not have failed (err=%s...)", err.Error()[:100])

+	}

+}

+

 func TestCmdStreamBad(t *testing.T) {

 	badCmd := exec.Command("/bin/sh", "-c", "echo hello; echo >&2 error couldn\\'t reverse the phase pulser; exit 1")

 	out, err := CmdStream(badCmd)