cr: wait the criu process properly

Signed-off-by: Andrey Vagin <avagin@openvz.org>

container_linux.go

@@ -356,10 +356,21 @@ func (c *linuxContainer) Restore(process *Process) error {
 	if err := cmd.Start(); err != nil {
 		return err
 	}
+
+	// cmd.Wait() waits cmd.goroutines which are used for proxying file descriptors.
+	// Here we want to wait only the CRIU process.
+	st, err := cmd.Process.Wait()
+	if err != nil {
+		return err
+	}
+	if !st.Success() {
+		return fmt.Errorf("criu failed: %s", st.String())
+	}
 	r, err := newRestoredProcess(pidfile, cmd)
 	if err != nil {
 		return err
 	}
+
 	// TODO: crosbymichael restore previous process information by saving the init process information in
 	// the conatiner's state file or separate process state files.
 	if err := c.updateState(r); err != nil {

restored_process.go

@@ -8,7 +8,6 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
-	"time"
 
 	"github.com/docker/libcontainer/system"
 )
@@ -18,21 +17,8 @@ func newRestoredProcess(pidfile string, criuCommand *exec.Cmd) (*restoredProcess
 		data []byte
 		err  error
 	)
-	// XXX The loop below should be replaced by a wait
+	data, err = ioutil.ReadFile(pidfile)
-	//     on CRIU to complete.  See the comment at the
+	if err != nil {
-	//     begining of Restore() in "container_linux.go.
-	for i := 0; i < 20; i++ {
-		data, err = ioutil.ReadFile(pidfile)
-		if err == nil {
-			break
-		}
-		if !os.IsNotExist(err) {
-			return nil, err
-		}
-		time.Sleep(100 * time.Millisecond)
-	}
-	// Did CRIU fail?
-	if os.IsNotExist(err) {
 		return nil, err
 	}
 	if len(data) == 0 {