cgroups: introduce helper macros

src/lxc/cgroups/cgfsng.c

@@ -1159,12 +1159,12 @@ __cgfsng_ops static void cgfsng_monitor_destroy(struct cgroup_ops *ops,
 			pivot_path = must_make_path(h->mountpoint,
 						    h->container_base_path,
 						    conf->cgroup_meta.dir,
-						    "lxc.pivot",
+						    PIVOT_CGROUP,
 						    "cgroup.procs", NULL);
 		else
 			pivot_path = must_make_path(h->mountpoint,
 						    h->container_base_path,
-						    "lxc.pivot",
+						    PIVOT_CGROUP,
 						    "cgroup.procs", NULL);
 
 		ret = mkdir_p(pivot_path, 0755);
@@ -2714,7 +2714,7 @@ __cgfsng_ops static bool cgfsng_data_init(struct cgroup_ops *ops)
 		return false;
 	}
 	ops->cgroup_pattern = must_copy_string(cgroup_pattern);
-	ops->monitor_pattern = must_copy_string("lxc.monitor");
+	ops->monitor_pattern = MONITOR_CGROUP;
 
 	return true;
 }

src/lxc/cgroups/cgroup.c

@@ -76,7 +76,6 @@ void cgroup_exit(struct cgroup_ops *ops)
 
 	free(ops->cgroup_pattern);
 	free(ops->container_cgroup);
-	free(ops->monitor_pattern);
 
 	for (it = ops->hierarchies; it && *it; it++) {
 		char **ctrlr;

src/lxc/cgroups/cgroup.h

@@ -28,6 +28,10 @@
 #include <stddef.h>
 #include <sys/types.h>
 
+#define PAYLOAD_CGROUP "lxc.payload"
+#define MONITOR_CGROUP "lxc.monitor"
+#define PIVOT_CGROUP "lxc.pivot"
+
 struct lxc_handler;
 struct lxc_conf;
 struct lxc_list;
@@ -96,6 +100,8 @@ struct cgroup_ops {
 	char **cgroup_use;
 	char *cgroup_pattern;
 	char *container_cgroup;
+
+	/* Static memory, do not free.*/
 	char *monitor_pattern;
 
 	/* @hierarchies