+
+char **cg_shorten_controllers(char **controllers) {
+ char **f, **t;
+
+ controllers = strv_uniq(controllers);
+
+ if (!controllers)
+ return controllers;
+
+ for (f = controllers, t = controllers; *f; f++) {
+ char *cc;
+
+ if (streq(*f, "systemd") || streq(*f, SYSTEMD_CGROUP_CONTROLLER)) {
+ free(*f);
+ continue;
+ }
+
+ cc = alloca(sizeof("/sys/fs/cgroup/") + strlen(*f));
+ strcpy(stpcpy(cc, "/sys/fs/cgroup/"), *f);
+
+ if (access(cc, F_OK) < 0) {
+ log_debug("Controller %s is not available, removing from controllers list.", *f);
+ free(*f);
+ continue;
+ }
+
+ *(t++) = *f;
+ }
+
+ *t = NULL;
+ return controllers;
+}