builder/amazon/chroot: block when obtaining lock [GH-689]

CHANGELOG.md

@@ -11,6 +11,8 @@ BUG FIXES:
 
 * core: Don't change background color on CLI anymore, making things look
   a tad nicer in some terminals.
+* builder/amazon/chroot: Block when obtaining file lock to allow
+  parallel builds. [GH-689]
 * builder/vmware: Cleanup of VMX keys works properly so cd-rom won't
   get stuck with ISO. [GH-685]
 

builder/amazon/chroot/lockfile_unix.go

@@ -14,13 +14,8 @@ const LOCK_NB = 4
 const LOCK_UN = 8
 
 func lockFile(f *os.File) error {
-	err := syscall.Flock(int(f.Fd()), LOCK_EX|LOCK_NB)
+	err := syscall.Flock(int(f.Fd()), LOCK_EX)
 	if err != nil {
-		errno, ok := err.(syscall.Errno)
-		if ok && errno == syscall.EWOULDBLOCK {
-			return errors.New("file already locked")
-		}
-
 		return err
 	}
 

builder/amazon/chroot/step_flock.go

@@ -39,7 +39,7 @@ func (s *StepFlock) Run(state multistep.StateBag) multistep.StepAction {
 
 	// LOCK!
 	if err := lockFile(f); err != nil {
-		err := fmt.Errorf("Error creating lock: %s", err)
+		err := fmt.Errorf("Error obtaining lock: %s", err)
 		state.Put("error", err)
 		ui.Error(err.Error())
 		return multistep.ActionHalt