Use common functions to handle file locking

 * lib/common.sh: implement
   - lock_open_write()
   - lock_open_read()
   - lock_close()
 * archbuild.in, makechrootpkg.in, mkarchroot.in: use said functions

This has two benefits:
 1. All programs using these methods gain the ability to inherit locks,
    something that only mkarchroot could do before.  This allows the
    commands to be more compos-able.
 2. It is more readable. File locking isn't obvious.

1 files changed, 1 insertions, 11 deletions

diff --git a/mkarchroot.in b/mkarchroot.in
index 76ad840..022943e 100644
--- a/mkarchroot.in
+++ b/mkarchroot.in
@@ -183,17 +183,7 @@ trap_chroot_umount () {
 }
 
 chroot_lock () {
-	# Only reopen the FD if it wasn't handed to us
-	if [[ $(readlink -f /dev/fd/9) != "${working_dir}.lock" ]]; then
-	  exec 9>"${working_dir}.lock"
-	fi
-
-	# Lock the chroot. Take note of the FD number.
-	if ! flock -n 9; then
-		stat_busy "Locking chroot"
-		flock 9
-		stat_done
-	fi
+	lock_open_write 9 "${working_dir}.lock" "Locking chroot"u
 }
 
 chroot_run() {