core: warn about left-over processes in cgroup on unit start

Now that we don't kill control processes anymore, let's at least warn
about any processes left-over in the unit cgroup at the moment of
starting the unit.

2 files changed, 30 insertions, 13 deletions

diff --git a/src/core/cgroup.c b/src/core/cgroup.c
index a0371512d..dd63fda23 100644
--- a/src/core/cgroup.c
+++ b/src/core/cgroup.c
@@ -1395,6 +1395,31 @@ int unit_watch_cgroup(Unit *u) {
         return 0;
 }
 
+int unit_pick_cgroup_path(Unit *u) {
+        _cleanup_free_ char *path = NULL;
+        int r;
+
+        assert(u);
+
+        if (u->cgroup_path)
+                return 0;
+
+        if (!UNIT_HAS_CGROUP_CONTEXT(u))
+                return -EINVAL;
+
+        path = unit_default_cgroup_path(u);
+        if (!path)
+                return log_oom();
+
+        r = unit_set_cgroup_path(u, path);
+        if (r == -EEXIST)
+                return log_unit_error_errno(u, r, "Control group %s exists already.", path);
+        if (r < 0)
+                return log_unit_error_errno(u, r, "Failed to set unit's control group path to %s: %m", path);
+
+        return 0;
+}
+
 static int unit_create_cgroup(
                 Unit *u,
                 CGroupMask target_mask,
@@ -1410,19 +1435,10 @@ static int unit_create_cgroup(
         if (!c)
                 return 0;
 
-        if (!u->cgroup_path) {
-                _cleanup_free_ char *path = NULL;
-
-                path = unit_default_cgroup_path(u);
-                if (!path)
-                        return log_oom();
-
-                r = unit_set_cgroup_path(u, path);
-                if (r == -EEXIST)
-                        return log_unit_error_errno(u, r, "Control group %s exists already.", path);
-                if (r < 0)
-                        return log_unit_error_errno(u, r, "Failed to set unit's control group path to %s: %m", path);
-        }
+        /* Figure out our cgroup path */
+        r = unit_pick_cgroup_path(u);
+        if (r < 0)
+                return r;
 
         /* First, create our own group */
         r = cg_create_everywhere(u->manager->cgroup_supported, target_mask, u->cgroup_path);
diff --git a/src/core/cgroup.h b/src/core/cgroup.h
index 1f0fefe9d..ab32a4919 100644
--- a/src/core/cgroup.h
+++ b/src/core/cgroup.h
@@ -169,6 +169,7 @@ void unit_update_cgroup_members_masks(Unit *u);
 
 char *unit_default_cgroup_path(Unit *u);
 int unit_set_cgroup_path(Unit *u, const char *path);
+int unit_pick_cgroup_path(Unit *u);
 
 int unit_realize_cgroup(Unit *u);
 void unit_release_cgroup(Unit *u);