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authorTejun Heo <tj@kernel.org>2012-11-09 09:12:29 -0800
committerTejun Heo <tj@kernel.org>2012-11-09 09:12:29 -0800
commita8638030f668884720b8f4456448d0ce33952b05 (patch)
tree2532b2ef9def879513fad0e304a6a9c98fa798f0 /kernel/cgroup.c
parent316eb661f125397d46f16f94e3c81ad3dc4c1233 (diff)
downloadop-kernel-dev-a8638030f668884720b8f4456448d0ce33952b05.zip
op-kernel-dev-a8638030f668884720b8f4456448d0ce33952b05.tar.gz
cgroup: add cgroup_subsys->post_create()
Currently, there's no way for a controller to find out whether a new cgroup finished all ->create() allocatinos successfully and is considered "live" by cgroup. This becomes a problem later when we add generic descendants walking to cgroup which can be used by controllers as controllers don't have a synchronization point where it can synchronize against new cgroups appearing in such walks. This patch adds ->post_create(). It's called after all ->create() succeeded and the cgroup is linked into the generic cgroup hierarchy. This plays the counterpart of ->pre_destroy(). When used in combination with the to-be-added generic descendant iterators, ->post_create() can be used to implement reliable state inheritance. It will be explained with the descendant iterators. v2: Added a paragraph about its future use w/ descendant iterators per Michal. v3: Forgot to add ->post_create() invocation to cgroup_load_subsys(). Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Glauber Costa <glommer@parallels.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 998ab59..26f2edb 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4059,10 +4059,15 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
if (err < 0)
goto err_remove;
- /* each css holds a ref to the cgroup's dentry */
- for_each_subsys(root, ss)
+ for_each_subsys(root, ss) {
+ /* each css holds a ref to the cgroup's dentry */
dget(dentry);
+ /* creation succeeded, notify subsystems */
+ if (ss->post_create)
+ ss->post_create(cgrp);
+ }
+
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
@@ -4280,6 +4285,9 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
ss->active = 1;
+ if (ss->post_create)
+ ss->post_create(&ss->root->top_cgroup);
+
/* this function shouldn't be used with modular subsystems, since they
* need to register a subsys_id, among other things */
BUG_ON(ss->module);
@@ -4389,6 +4397,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
ss->active = 1;
+ if (ss->post_create)
+ ss->post_create(&ss->root->top_cgroup);
+
/* success! */
mutex_unlock(&cgroup_mutex);
return 0;
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