lib/common.sh: Introduce locking helper functions

Reduces code duplication.

With makechrootpkg not calling mkarchroot anymore,
the lock handover protocol is unneeded.

arch-nspawn does not do any locking, so add protection to archbuild.

archbuild.in

@@ -51,12 +51,7 @@ if ${clean_first} || [[ ! -d "${chroots}/${repo}-${arch}" ]]; then
 		[[ -d $copy ]] || continue
 		msg2 "Deleting chroot copy '$(basename "${copy}")'..."
 
-		exec 9>"$copydir.lock"
-		if ! flock -n 9; then
-			stat_busy "Locking chroot copy '$copy'"
-			flock 9
-			stat_done
-		fi
+		lock 9 "$copydir.lock" "Locking chroot copy '$copy'"
 
 		if [[ "$(stat -f -c %T "${copy}")" == btrfs ]]; then
 			{ type -P btrfs && btrfs subvolume delete "${copy}"; } &>/dev/null
@@ -73,6 +68,7 @@ if ${clean_first} || [[ ! -d "${chroots}/${repo}-${arch}" ]]; then
 		"${chroots}/${repo}-${arch}/root" \
 		"${base_packages[@]}" || abort
 else
+	lock 9 "${chroots}/${repo}-${arch}/root.lock" "Locking clean chroot"
 	setarch ${arch} arch-nspawn \
 		-C "@pkgdatadir@/pacman-${repo}.conf" \
 		-M "@pkgdatadir@/makepkg-${arch}.conf" \

lib/common.sh

@@ -130,3 +130,27 @@ get_full_version() {
 		fi
 	fi
 }
+
+##
+#  usage : lock( $fd, $file, $message )
+##
+lock() {
+	eval "exec $1>"'"$2"'
+	if ! flock -n $1; then
+		stat_busy "$3"
+		flock $1
+		stat_done
+	fi
+}
+
+##
+#  usage : slock( $fd, $file, $message )
+##
+slock() {
+	eval "exec $1>"'"$2"'
+	if ! flock -sn $1; then
+		stat_busy "$3"
+		flock -s $1
+		stat_done
+	fi
+}

makechrootpkg.in

@@ -120,24 +120,12 @@ umask 0022
 chroottype=$(stat -f -c %T "$chrootdir")
 
 # Lock the chroot we want to use. We'll keep this lock until we exit.
-# Note this is the same FD number as in mkarchroot
-exec 9>"$copydir.lock"
-if ! flock -n 9; then
-	stat_busy "Locking chroot copy [$copy]"
-	flock 9
-	stat_done
-fi
+lock 9 "$copydir.lock" "Locking chroot copy [$copy]"
 
 if [[ ! -d $copydir ]] || $clean_first; then
 	# Get a read lock on the root chroot to make
 	# sure we don't clone a half-updated chroot
-	exec 8>"$chrootdir/root.lock"
-
-	if ! flock -sn 8; then
-		stat_busy "Locking clean chroot"
-		flock -s 8
-		stat_done
-	fi
+	slock 8 "$chrootdir/root.lock" "Locking clean chroot"
 
 	stat_busy "Creating clean working copy [$copy]"
 	if [[ "$chroottype" == btrfs ]]; then

mkarchroot.in

@@ -49,29 +49,13 @@ else
 	cache_dirs=(${cache_dir})
 fi
 
-# {{{ functions
-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
-}
-# }}}
-
 umask 0022
 
 [[ -e $working_dir ]] && die "Working directory '$working_dir' already exists"
 
 mkdir -p "$working_dir"
 
-chroot_lock
+lock 9 "${working_dir}.lock" "Locking chroot"
 
 if [[ $(stat -f -c %T "$working_dir") == btrfs ]]; then
 	rmdir "$working_dir"