procd: introduce procd_lock for init script protection

Use flock to protect init script from concurrent execution
(of the same script).
Important for services which generate native config files.

Signed-off-by: Roman Yeryomin <roman@advem.lv>
Signed-off-by: Andrejs Hanins <ahanins@gmail.com>

package/system/procd/files/procd.sh

@@ -38,6 +38,20 @@
 PROCD_RELOAD_DELAY=1000
 _PROCD_SERVICE=
 
+procd_lock() {
+	local basescript=$(readlink "$initscript")
+	local service_name="$(basename ${basescript:-$initscript})"
+
+	flock -n 1000 &> /dev/null
+	if [ "$?" != "0" ]; then
+		exec 1000>/var/lock/procd_${service_name}.lock
+		flock 1000
+		if [ "$?" != "0" ]; then
+			logger "warning: procd flock for $service_name failed"
+		fi
+	fi
+}
+
 _procd_call() {
 	local old_cb
 
@@ -47,6 +61,7 @@ _procd_call() {
 }
 
 _procd_wrapper() {
+	procd_lock
 	while [ -n "$1" ]; do
 		eval "$1() { _procd_call _$1 \"\$@\"; }"
 		shift