From 298f884a265c1c4b30cce7467650cc4a165a284e Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 5 Nov 2013 22:14:52 +0100
Subject: [PATCH] cgroup: run PID 1 in the root cgroup

This way cleaning up the cgroup tree on shutdown is a lot easier since
we are in the root dir. Also PID 1 was previously artificially placed in
system.slice, even though our rule actually was not to have processes in
slices. The root slice otoh is magic anyway, so having PID 1 in there
sounds less surprising.

Of course, this means that PID is scheduled against the three top-level
slices.
---
 src/core/cgroup.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index 8bf4d89..42c0b3f 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -589,8 +589,8 @@ pid_t unit_search_main_pid(Unit *u) {
 
 int manager_setup_cgroup(Manager *m) {
         _cleanup_free_ char *path = NULL;
+        char *e;
         int r;
-        char *e, *a;
 
         assert(m);
 
@@ -610,9 +610,13 @@ int manager_setup_cgroup(Manager *m) {
                 return r;
         }
 
-        /* Already in /system.slice? If so, let's cut this off again */
+        /* LEGACY: Already in /system.slice? If so, let's cut this
+         * off. This is to support live upgrades from older systemd
+         * versions where PID 1 was moved there. */
         if (m->running_as == SYSTEMD_SYSTEM) {
                 e = endswith(m->cgroup_root, "/" SPECIAL_SYSTEM_SLICE);
+                if (!e)
+                        e = endswith(m->cgroup_root, "/system");
                 if (e)
                         *e = 0;
         }
@@ -643,12 +647,8 @@ int manager_setup_cgroup(Manager *m) {
                         log_debug("Release agent already installed.");
         }
 
-        /* 4. Realize the system slice and put us in there */
-        if (m->running_as == SYSTEMD_SYSTEM) {
-                a = strappenda(m->cgroup_root, "/" SPECIAL_SYSTEM_SLICE);
-                r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, a, 0);
-        } else
-                r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, m->cgroup_root, 0);
+        /* 4. Make sure we are in the root cgroup */
+        r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, m->cgroup_root, 0);
         if (r < 0) {
                 log_error("Failed to create root cgroup hierarchy: %s", strerror(-r));
                 return r;