linux-stable.git/include/linux/cgroup.h, branch v3.8.3

cgroup: remove obsolete guarantee from cgroup_task_migrate.

2012-11-20T14:44:58+00:00

'guarantee' is already removed from cgroup_task_migrate, so remove
the corresponding comments. Some other typos in cgroup are also
changed.

Cc: Tejun Heo 
Cc: Li Zefan 
Signed-off-by: Tao Ma 
Signed-off-by: Tejun Heo

cgroup: add cgroup->id

2012-11-19T17:02:12+00:00

With the introduction of generic cgroup hierarchy iterators, css_id is
being phased out.  It was unnecessarily complex, id'ing the wrong
thing (cgroups need IDs, not CSSes) and has other oddities like not
being available at ->css_alloc().

This patch adds cgroup->id, which is a simple per-hierarchy
ida-allocated ID which is assigned before ->css_alloc() and released
after ->css_free().

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan 
Acked-by: Neil Horman

cgroup, cpuset: remove cgroup_subsys->post_clone()

2012-11-19T16:13:39+00:00

Currently CGRP_CPUSET_CLONE_CHILDREN triggers ->post_clone().  Now
that clone_children is cpuset specific, there's no reason to have this
rather odd option activation mechanism in cgroup core.  cpuset can
check the flag from its ->css_allocate() and take the necessary
action.

Move cpuset_post_clone() logic to the end of cpuset_css_alloc() and
remove cgroup_subsys->post_clone().

Loosely based on Glauber's "generalize post_clone into post_create"
patch.

Signed-off-by: Tejun Heo 
Original-patch-by: Glauber Costa 
Original-patch: <1351686554-22592-2-git-send-email-glommer@parallels.com>
Acked-by: Serge E. Hallyn 
Acked-by: Li Zefan 
Cc: Glauber Costa

cgroup: s/CGRP_CLONE_CHILDREN/CGRP_CPUSET_CLONE_CHILDREN/

2012-11-19T16:13:38+00:00

clone_children is only meaningful for cpuset and will stay that way.
Rename the flag to reflect that and update documentation.  Also, drop
clone_children() wrapper in cgroup.c.  The thin wrapper is used only a
few times and one of them will go away soon.

Signed-off-by: Tejun Heo 
Acked-by: Serge E. Hallyn 
Acked-by: Li Zefan 
Cc: Glauber Costa

cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free()

2012-11-19T16:13:38+00:00

Rename cgroup_subsys css lifetime related callbacks to better describe
what their roles are.  Also, update documentation.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan

cgroup: allow ->post_create() to fail

2012-11-19T16:13:38+00:00

There could be cases where controllers want to do initialization
operations which may fail from ->post_create().  This patch makes
->post_create() return -errno to indicate failure and online_css()
relay such failures.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan 
Cc: Glauber Costa

cgroup: introduce CSS_ONLINE flag and on/offline_css() helpers

2012-11-19T16:13:37+00:00

New helpers on/offline_css() respectively wrap ->post_create() and
->pre_destroy() invocations.  online_css() sets CSS_ONLINE after
->post_create() is complete and offline_css() invokes ->pre_destroy()
iff CSS_ONLINE is set and clears it while also handling the temporary
dropping of cgroup_mutex.

This patch doesn't introduce any behavior change at the moment but
will be used to improve cgroup_create() failure path and allow
->post_create() to fail.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan

cgroup: make CSS_* flags bit masks instead of bit positions

2012-11-19T16:13:36+00:00

Currently, CSS_* flags are defined as bit positions and manipulated
using atomic bitops.  There's no reason to use atomic bitops for them
and bit positions are clunkier to deal with than bit masks.  Make
CSS_* bit masks instead and use the usual C bitwise operators to
access them.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan

cgroup: cgroup->dentry isn't a RCU pointer

2012-11-19T16:13:36+00:00

cgroup->dentry is marked and used as a RCU pointer; however, it isn't
one - the final dentry put doesn't go through call_rcu().  cgroup and
dentry share the same RCU freeing rule via synchronize_rcu() in
cgroup_diput() (kfree_rcu() used on cgrp is unnecessary).  If cgrp is
accessible under RCU read lock, so is its dentry and dereferencing
cgrp->dentry doesn't need any further RCU protection or annotation.

While not being accurate, before the previous patch, the RCU accessors
served a purpose as memory barriers - cgroup->dentry used to be
assigned after the cgroup was made visible to cgroup_path(), so the
assignment and dereferencing in cgroup_path() needed the memory
barrier pair.  Now that list_add_tail_rcu() happens after
cgroup->dentry is assigned, this no longer is necessary.

Remove the now unnecessary and misleading RCU annotations from
cgroup->dentry.  To make up for the removal of rcu_dereference_check()
in cgroup_path(), add an explicit rcu_lockdep_assert(), which asserts
the dereference rule of @cgrp, not cgrp->dentry.

Signed-off-by: Tejun Heo 
Acked-by: Li Zefan

cgroup: implement generic child / descendant walk macros

2012-11-09T17:12:29+00:00

Currently, cgroup doesn't provide any generic helper for walking a
given cgroup's children or descendants.  This patch adds the following
three macros.

* cgroup_for_each_child() - walk immediate children of a cgroup.

* cgroup_for_each_descendant_pre() - visit all descendants of a cgroup
  in pre-order tree traversal.

* cgroup_for_each_descendant_post() - visit all descendants of a
  cgroup in post-order tree traversal.

All three only require the user to hold RCU read lock during
traversal.  Verifying that each iterated cgroup is online is the
responsibility of the user.  When used with proper synchronization,
cgroup_for_each_descendant_pre() can be used to propagate state
updates to descendants in reliable way.  See comments for details.

v2: s/config/state/ in commit message and comments per Michal.  More
    documentation on synchronization rules.

Signed-off-by: Tejun Heo 
Reviewed-by: KAMEZAWA Hiroyuki 
Reviewed-by: Michal Hocko 
Acked-by: Li Zefan