linux/Documentation/cgroups/cgroups.txt, branch v3.2.23

Documentation: update cgroups notes

2011-11-04T19:01:46Z

- ns cgroup has been removed. - it's true moving a task to another cgroup can fail. Signed-off-by: Li Zefan Acked-by: Paul Menage Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

Documentation: fix cgroup typos and formatting

2011-06-16T04:52:50Z

Fix format and spelling. Signed-off-by: Jörg Sommer Acked-by: Paul Menage Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

Documentation: update cgroupfs mount point

2011-06-16T04:52:50Z

According to commit 676db4af0430 ("cgroupfs: create /sys/fs/cgroup to mount cgroupfs on") the canonical mountpoint for the cgroup filesystem is /sys/fs/cgroup. Hence, this should be used in the documentation. Signed-off-by: Jörg Sommer Acked-by: Paul Menage Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

cgroup: remove the ns_cgroup

2011-05-27T00:12:34Z

The ns_cgroup is an annoying cgroup at the namespace / cgroup frontier and leads to some problems: * cgroup creation is out-of-control * cgroup name can conflict when pids are looping * it is not possible to have a single process handling a lot of namespaces without falling in a exponential creation time * we may want to create a namespace without creating a cgroup The ns_cgroup was replaced by a compatibility flag 'clone_children', where a newly created cgroup will copy the parent cgroup values. The userspace has to manually create a cgroup and add a task to the 'tasks' file. This patch removes the ns_cgroup as suggested in the following thread: https://lists.linux-foundation.org/pipermail/containers/2009-June/018616.html The 'cgroup_clone' function is removed because it is no longer used. This is a userspace-visible change. Commit 45531757b45c ("cgroup: notify ns_cgroup deprecated") (merged into 2.6.27) caused the kernel to emit a printk warning users that the feature is planned for removal. Since that time we have heard from XXX users who were affected by this. Signed-off-by: Daniel Lezcano Signed-off-by: Serge E. Hallyn Cc: Eric W. Biederman Cc: Jamal Hadi Salim Reviewed-by: Li Zefan Acked-by: Paul Menage Acked-by: Matt Helsley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroups: make procs file writable

2011-05-27T00:12:34Z

Make procs file writable to move all threads by tgid at once. Add functionality that enables users to move all threads in a threadgroup at once to a cgroup by writing the tgid to the 'cgroup.procs' file. This current implementation makes use of a per-threadgroup rwsem that's taken for reading in the fork() path to prevent newly forking threads within the threadgroup from "escaping" while the move is in progress. Signed-off-by: Ben Blum Cc: "Eric W. Biederman" Cc: Li Zefan Cc: Matt Helsley Reviewed-by: Paul Menage Cc: Oleg Nesterov Cc: David Rientjes Cc: Miao Xie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroups: add per-thread subsystem callbacks

2011-05-27T00:12:34Z

Add cgroup subsystem callbacks for per-thread attachment in atomic contexts Add can_attach_task(), pre_attach(), and attach_task() as new callbacks for cgroups's subsystem interface. Unlike can_attach and attach, these are for per-thread operations, to be called potentially many times when attaching an entire threadgroup. Also, the old "bool threadgroup" interface is removed, as replaced by this. All subsystems are modified for the new interface - of note is cpuset, which requires from/to nodemasks for attach to be globally scoped (though per-cpuset would work too) to persist from its pre_attach to attach_task and attach. This is a pre-patch for cgroup-procs-writable.patch. Signed-off-by: Ben Blum Cc: "Eric W. Biederman" Cc: Li Zefan Cc: Matt Helsley Reviewed-by: Paul Menage Cc: Oleg Nesterov Cc: David Rientjes Cc: Miao Xie Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Documentation: update cgroups info user groups names

2011-04-05T00:51:47Z

Update suitable words to explain / understand cgroups contents. Signed-off-by: Geunsik Lim Cc: Paul Menage Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

Documentation: update cgroup pid and cpuset information

2011-03-16T17:47:04Z

The cgroup documentation does not specify how a process can be removed from a particular group. This patch adds a note at the end of the simple example about how this is done. Also, some cgroups (like cpusets) require user input before a new group can be used. This is noted in the patch as well. Signed-off-by: Eric B Munson Acked-by: Paul Menage Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds

cgroups: remove deprecated subsystem from examples.

2011-01-13T16:03:16Z

The 'ns' cgroup is considered deprecated. Change the cgroup subsystem used in the examples of the cgroup documentation from 'ns' to 'blkio'. Signed-off-by: Trevor Woerner Acked-by: Li Zefan Acked-by: Paul Menage Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroup: add clone_children control file

2010-10-28T01:03:09Z

The ns_cgroup is a control group interacting with the namespaces. When a new namespace is created, a corresponding cgroup is automatically created too. The cgroup name is the pid of the process who did 'unshare' or the child of 'clone'. This cgroup is tied with the namespace because it prevents a process to escape the control group and use the post_clone callback, so the child cgroup inherits the values of the parent cgroup. Unfortunately, the more we use this cgroup and the more we are facing problems with it: (1) when a process unshares, the cgroup name may conflict with a previous cgroup with the same pid, so unshare or clone return -EEXIST (2) the cgroup creation is out of control because there may have an application creating several namespaces where the system will automatically create several cgroups in his back and let them on the cgroupfs (eg. a vrf based on the network namespace). (3) the mix of (1) and (2) force an administrator to regularly check and clean these cgroups. This patchset removes the ns_cgroup by adding a new flag to the cgroup and the cgroupfs mount option. It enables the copy of the parent cgroup when a child cgroup is created. We can then safely remove the ns_cgroup as this flag brings a compatibility. We have now to manually create and add the task to a cgroup, which is consistent with the cgroup framework. This patch: Sent as an answer to a previous thread around the ns_cgroup. https://lists.linux-foundation.org/pipermail/containers/2009-June/018627.html It adds a control file 'clone_children' for a cgroup. This control file is a boolean specifying if the child cgroup should be a clone of the parent cgroup or not. The default value is 'false'. This flag makes the child cgroup to call the post_clone callback of all the subsystem, if it is available. At present, the cpuset is the only one which had implemented the post_clone callback. The option can be set at mount time by specifying the 'clone_children' mount option. Signed-off-by: Daniel Lezcano Signed-off-by: Serge E. Hallyn Cc: Eric W. Biederman Acked-by: Paul Menage Reviewed-by: Li Zefan Cc: Jamal Hadi Salim Cc: Matt Helsley Acked-by: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds