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Revert "cgroup: remove bind() method from cgroup_subsys."

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This reverts commit 84cfb6ab48.  There
are scheduled changes which make use of the removed callback.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rami Rosen <ramirose@gmail.com>
Cc: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-04-12 10:29:04 -07:00
parent ef824fa129
commit 26d5bbe5ba
3 changed files with 21 additions and 5 deletions
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20
Documentation/cgroups/cgroups.txt
View File

@ -211,9 +211,10 @@ matches, and any of the requested subsystems are in use in an existing
hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy
is activated, associated with the requested subsystems.
It's not possible to bind a new subsystem to an active cgroup
hierarchy, or to unbind a subsystem from an active cgroup
hierarchy.
It's not currently possible to bind a new subsystem to an active
cgroup hierarchy, or to unbind a subsystem from an active cgroup
hierarchy. This may be possible in future, but is fraught with nasty
error-recovery issues.
When a cgroup filesystem is unmounted, if there are any
child cgroups created below the top-level cgroup, that hierarchy
@ -381,8 +382,10 @@ To Specify a hierarchy's release_agent:
Note that specifying 'release_agent' more than once will return failure.
Note that changing the set of subsystems is only supported when the
hierarchy consists of a single (root) cgroup.
Note that changing the set of subsystems is currently only supported
when the hierarchy consists of a single (root) cgroup. Supporting
the ability to arbitrarily bind/unbind subsystems from an existing
cgroup hierarchy is intended to be implemented in the future.
Then under /sys/fs/cgroup/rg1 you can find a tree that corresponds to the
tree of the cgroups in the system. For instance, /sys/fs/cgroup/rg1
@ -640,6 +643,13 @@ void exit(struct task_struct *task)
Called during task exit.
void bind(struct cgroup *root)
(cgroup_mutex held by caller)
Called when a cgroup subsystem is rebound to a different hierarchy
and root cgroup. Currently this will only involve movement between
the default hierarchy (which never has sub-cgroups) and a hierarchy
that is being created/destroyed (and hence has no sub-cgroups).
4. Extended attribute usage
===========================

2
include/linux/cgroup.h
View File

@ -484,6 +484,8 @@ struct cgroup_subsys {
void (*fork)(struct task_struct *task);
void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
struct task_struct *task);
void (*bind)(struct cgroup *root);
int subsys_id;
int active;
int disabled;

4
kernel/cgroup.c
View File

@ -1091,12 +1091,16 @@ static int rebind_subsystems(struct cgroupfs_root *root,
cgrp->subsys[i]->cgroup = cgrp;
list_move(&ss->sibling, &root->subsys_list);
ss->root = root;
if (ss->bind)
ss->bind(cgrp);
/* refcount was already taken, and we're keeping it */
} else if (bit & removed_mask) {
/* We're removing this subsystem */
BUG_ON(ss == NULL);
BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
if (ss->bind)
ss->bind(dummytop);
dummytop->subsys[i]->cgroup = dummytop;
cgrp->subsys[i] = NULL;
subsys[i]->root = &rootnode;