From 2dad0cdca76021765cc36e8c2974132e22ec4fb4 Mon Sep 17 00:00:00 2001
From: Mitchell Hashimoto <mitchell.hashimoto@gmail.com>
Date: Fri, 6 Dec 2013 18:28:48 -0800
Subject: [PATCH] builder/amazon/chroot: block when obtaining lock [GH-689]

---
 CHANGELOG.md                           | 2 ++
 builder/amazon/chroot/lockfile_unix.go | 7 +------
 builder/amazon/chroot/step_flock.go    | 2 +-
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 22bea8053..6f7d06a3e 100644
--- a/CHANGELOG.md
+++ b/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]
 
diff --git a/builder/amazon/chroot/lockfile_unix.go b/builder/amazon/chroot/lockfile_unix.go
index f84ea0d57..1a389adb4 100644
--- a/builder/amazon/chroot/lockfile_unix.go
+++ b/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
 	}
 
diff --git a/builder/amazon/chroot/step_flock.go b/builder/amazon/chroot/step_flock.go
index 989bd3930..9f7ca54b8 100644
--- a/builder/amazon/chroot/step_flock.go
+++ b/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