core: check for redundant operation before doing allocation

[thirdparty/systemd.git] / src / core / cgroup.c

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index ad67ba043892db86d64cc9442ae5a3121f9bad1a..01d72a390817389ad6feb7cb22eca65b4c9d22c7 100644 (file)
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1568,15 +1568,14 @@ int unit_set_cgroup_path(Unit *u, const char *path) {
 
         assert(u);
 
+        if (streq_ptr(u->cgroup_path, path))
+                return 0;
+
         if (path) {
                 p = strdup(path);
                 if (!p)
                         return -ENOMEM;
-        } else
-                p = NULL;
-
-        if (streq_ptr(u->cgroup_path, p))
-                return 0;
+        }
 
         if (p) {
                 r = hashmap_put(u->manager->cgroup_unit, p, u);
@@ -1585,7 +1584,6 @@ int unit_set_cgroup_path(Unit *u, const char *path) {
         }
 
         unit_release_cgroup(u);
-
         u->cgroup_path = TAKE_PTR(p);
 
         return 1;
@@ -2606,6 +2604,9 @@ int manager_setup_cgroup(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to create cgroup empty event source: %m");
 
+        /* Schedule cgroup empty checks early, but after having processed service notification messages or
+         * SIGCHLD signals, so that a cgroup running empty is always just the last safety net of
+         * notification, and we collected the metadata the notification and SIGCHLD stuff offers first. */
         r = sd_event_source_set_priority(m->cgroup_empty_event_source, SD_EVENT_PRIORITY_NORMAL-5);
         if (r < 0)
                 return log_error_errno(r, "Failed to set priority of cgroup empty event source: %m");
@@ -2632,9 +2633,10 @@ int manager_setup_cgroup(Manager *m) {
                 if (r < 0)
                         return log_error_errno(r, "Failed to watch control group inotify object: %m");
 
-                /* Process cgroup empty notifications early, but after service notifications and SIGCHLD. Also
-                 * see handling of cgroup agent notifications, for the classic cgroup hierarchy support. */
-                r = sd_event_source_set_priority(m->cgroup_inotify_event_source, SD_EVENT_PRIORITY_NORMAL-4);
+                /* Process cgroup empty notifications early. Note that when this event is dispatched it'll
+                 * just add the unit to a cgroup empty queue, hence let's run earlier than that. Also see
+                 * handling of cgroup agent notifications, for the classic cgroup hierarchy support. */
+                r = sd_event_source_set_priority(m->cgroup_inotify_event_source, SD_EVENT_PRIORITY_NORMAL-9);
                 if (r < 0)
                         return log_error_errno(r, "Failed to set priority of inotify event source: %m");