---

yaml
---
r: 120747
b: refs/heads/master
c: 94d6a5f
h: refs/heads/master
i:
  120745: 73c5d98
  120743: 3f5e5cc
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 7657d90497f98426af17f0ac633a9b335bb7a8fb
+refs/heads/master: 94d6a5f7341ebaff53d4e41cc81fab37f0d9fbed

trunk/Documentation/scheduler/sched-design-CFS.txt

@@ -273,3 +273,24 @@ task groups and modify their CPU share using the "cgroups" pseudo filesystem.
 
 	# #Launch gmplayer (or your favourite movie player)
 	# echo <movie_player_pid> > multimedia/tasks
+
+8. Implementation note: user namespaces
+
+User namespaces are intended to be hierarchical.  But they are currently
+only partially implemented.  Each of those has ramifications for CFS.
+
+First, since user namespaces are hierarchical, the /sys/kernel/uids
+presentation is inadequate.  Eventually we will likely want to use sysfs
+tagging to provide private views of /sys/kernel/uids within each user
+namespace.
+
+Second, the hierarchical nature is intended to support completely
+unprivileged use of user namespaces.  So if using user groups, then
+we want the users in a user namespace to be children of the user
+who created it.
+
+That is currently unimplemented.  So instead, every user in a new
+user namespace will receive 1024 shares just like any user in the
+initial user namespace.  Note that at the moment creation of a new
+user namespace requires each of CAP_SYS_ADMIN, CAP_SETUID, and
+CAP_SETGID.

trunk/kernel/user.c

@@ -239,7 +239,13 @@ static struct kobj_type uids_ktype = {
 	.release = uids_release,
 };
 
-/* create /sys/kernel/uids/<uid>/cpu_share file for this user */
+/*
+ * Create /sys/kernel/uids/<uid>/cpu_share file for this user
+ * We do not create this file for users in a user namespace (until
+ * sysfs tagging is implemented).
+ *
+ * See Documentation/scheduler/sched-design-CFS.txt for ramifications.
+ */
 static int uids_user_create(struct user_struct *up)
 {
 	struct kobject *kobj = &up->kobj;