| Message ID | 20121107171508.GF2660@mtj.dyndns.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Wed 07-11-12 09:15:08, Tejun Heo wrote: [...] > 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. Thanks
(2012/11/08 2:15), Tejun Heo wrote: > 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. > > Signed-off-by: Tejun Heo <tj@kernel.org> > Acked-by: Michal Hocko <mhocko@suse.cz> > Cc: Glauber Costa <glommer@parallels.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -438,6 +438,7 @@ int cgroup_taskset_size(struct cgroup_ta struct cgroup_subsys { struct cgroup_subsys_state *(*create)(struct cgroup *cgrp); + void (*post_create)(struct cgroup *cgrp); void (*pre_destroy)(struct cgroup *cgrp); void (*destroy)(struct cgroup *cgrp); int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset); --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4060,10 +4060,15 @@ static long cgroup_create(struct cgroup 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)); @@ -4281,6 +4286,9 @@ static void __init cgroup_init_subsys(st 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);
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. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Glauber Costa <glommer@parallels.com> --- If you can explain it better, please be my guest. Thanks. include/linux/cgroup.h | 1 + kernel/cgroup.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html