From: Li Zefan <lizefan@huawei.com>
To: Tejun Heo <tj@kernel.org>
Cc: <containers@lists.linux-foundation.org>,
<cgroups@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 07/14] cgroup: reorganize css init / exit paths
Date: Mon, 12 Aug 2013 10:47:33 +0800 [thread overview]
Message-ID: <52084CC5.8050207@huawei.com> (raw)
In-Reply-To: <1375992831-4650-8-git-send-email-tj@kernel.org>
> /* invoke ->css_online() on a new CSS and mark it online if successful */
> -static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +static int online_css(struct cgroup_subsys_state *css)
> {
> - struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
> + struct cgroup_subsys *ss = css->ss;
> int ret = 0;
>
> lockdep_assert_held(&cgroup_mutex);
> @@ -4342,9 +4340,9 @@ static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
> }
>
> /* if the CSS is online, invoke ->css_offline() on it and mark it offline */
> -static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +static void offline_css(struct cgroup_subsys_state *css)
> {
> - struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
> + struct cgroup_subsys *ss = css->ss;
>
> lockdep_assert_held(&cgroup_mutex);
>
> @@ -4442,10 +4440,10 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> goto err_free_all;
> }
>
> - init_cgroup_css(css, ss, cgrp);
> + init_css(css, ss, cgrp);
>
> if (ss->use_id) {
> - err = alloc_css_id(ss, parent, cgrp);
> + err = alloc_css_id(css);
> if (err)
> goto err_free_all;
> }
> @@ -4467,20 +4465,18 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
> root->number_of_cgroups++;
>
> - /* each css holds a ref to the cgroup's dentry and the parent css */
> + /* hold a ref to the parent's dentry */
> + dget(parent->dentry);
> +
> for_each_root_subsys(root, ss) {
> struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
>
> + /* each css holds a ref to the cgroup and the parent css */
> dget(dentry);
> percpu_ref_get(&css->parent->refcnt);
We called dget() and percpu_ref_get() for each css unconditionally...
> - }
>
> - /* hold a ref to the parent's dentry */
> - dget(parent->dentry);
> -
> - /* creation succeeded, notify subsystems */
> - for_each_root_subsys(root, ss) {
> - err = online_css(ss, cgrp);
> + /* creation succeeded, notify subsystems */
> + err = online_css(css);
> if (err)
> goto err_destroy;
but now dget() and percpu_ref_get() may not be called for some css's,
but the code in failure path is not updated accordingly, which seems
wrong.
>
> @@ -4700,7 +4696,7 @@ static void cgroup_offline_fn(struct work_struct *work)
> * initate destruction.
> */
> for_each_root_subsys(cgrp->root, ss)
> - offline_css(ss, cgrp);
> + offline_css(cgroup_css(cgrp, ss->subsys_id));
>
> /*
> * Put the css refs from cgroup_destroy_locked(). Each css holds
> @@ -4778,7 +4774,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
> css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss->subsys_id));
> /* We don't handle early failures gracefully */
> BUG_ON(IS_ERR(css));
> - init_cgroup_css(css, ss, cgroup_dummy_top);
> + init_css(css, ss, cgroup_dummy_top);
>
> /* Update the init_css_set to contain a subsys
> * pointer to this state - since the subsystem is
> @@ -4793,7 +4789,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
> * need to invoke fork callbacks here. */
> BUG_ON(!list_empty(&init_task.tasks));
>
> - BUG_ON(online_css(ss, cgroup_dummy_top));
> + BUG_ON(online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id)));
>
> mutex_unlock(&cgroup_mutex);
>
> @@ -4866,8 +4862,8 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
> ss->root = &cgroup_dummy_root;
>
> /* our new subsystem will be attached to the dummy hierarchy. */
> - init_cgroup_css(css, ss, cgroup_dummy_top);
> - /* init_idr must be after init_cgroup_css because it sets css->id. */
> + init_css(css, ss, cgroup_dummy_top);
> + /* init_idr must be after init_css() because it sets css->id. */
> if (ss->use_id) {
> ret = cgroup_init_idr(ss, css);
> if (ret)
> @@ -4897,7 +4893,7 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
> }
> write_unlock(&css_set_lock);
>
> - ret = online_css(ss, cgroup_dummy_top);
> + ret = online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
> if (ret)
> goto err_unload;
>
> @@ -4936,7 +4932,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
>
> mutex_lock(&cgroup_mutex);
>
> - offline_css(ss, cgroup_dummy_top);
> + offline_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
>
> if (ss->use_id)
> idr_destroy(&ss->idr);
> @@ -5588,20 +5584,16 @@ static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
> return 0;
> }
>
> -static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
> - struct cgroup *child)
> +static int alloc_css_id(struct cgroup_subsys_state *child_css)
> {
> - int subsys_id, i, depth = 0;
> - struct cgroup_subsys_state *parent_css, *child_css;
> + struct cgroup_subsys_state *parent_css = css_parent(child_css);
> struct css_id *child_id, *parent_id;
> + int i, depth;
>
> - subsys_id = ss->subsys_id;
> - parent_css = cgroup_css(parent, subsys_id);
> - child_css = cgroup_css(child, subsys_id);
> parent_id = rcu_dereference_protected(parent_css->id, true);
> depth = parent_id->depth + 1;
>
> - child_id = get_new_cssid(ss, depth);
> + child_id = get_new_cssid(child_css->ss, depth);
> if (IS_ERR(child_id))
> return PTR_ERR(child_id);
>
>
next prev parent reply other threads:[~2013-08-12 2:53 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-08 20:13 [PATCHSET cgroup/for-3.12] cgroup: decouple cgroup_subsys_state lifetime from that of cgroup Tejun Heo
2013-08-08 20:13 ` [PATCH 01/14] cgroup: always use cgroup_css() Tejun Heo
2013-08-08 20:13 ` [PATCH 02/14] cgroup: rename cgroup_subsys_state->dput_work and its callback function Tejun Heo
2013-08-08 20:13 ` [PATCH 03/14] cgroup: add cgroup_subsys_state->parent Tejun Heo
2013-08-08 20:13 ` [PATCH 04/14] cgroup: cgroup_css_from_dir() now should be called with RCU read locked Tejun Heo
2013-08-08 20:13 ` [PATCH 05/14] cgroup: make cgroup_file_open() rcu_read_lock() around cgroup_css() and add cfent->css Tejun Heo
2013-08-08 20:13 ` [PATCH 06/14] cgroup: add __rcu modifier to cgroup->subsys[] Tejun Heo
2013-08-08 20:13 ` [PATCH 07/14] cgroup: reorganize css init / exit paths Tejun Heo
2013-08-12 2:47 ` Li Zefan [this message]
2013-08-12 13:39 ` Tejun Heo
2013-08-12 13:40 ` [PATCH v2 " Tejun Heo
2013-08-08 20:13 ` [PATCH 08/14] cgroup: move cgroup->subsys[] assignment to online_css() Tejun Heo
2013-08-14 0:27 ` [PATCH v2 " Tejun Heo
2013-08-08 20:13 ` [PATCH 09/14] cgroup: bounce cgroup_subsys_state ref kill confirmation to a work item Tejun Heo
2013-08-08 20:13 ` [PATCH 10/14] cgroup: replace cgroup->css_kill_cnt with ->nr_css Tejun Heo
2013-08-08 20:13 ` [PATCH 11/14] cgroup: decouple cgroup_subsys_state destruction from cgroup destruction Tejun Heo
2013-08-08 20:13 ` [PATCH 12/14] cgroup: factor out kill_css() Tejun Heo
2013-08-08 20:13 ` [PATCH 13/14] cgroup: move subsys file removal to kill_css() Tejun Heo
2013-08-08 20:13 ` [PATCH 14/14] cgroup: RCU protect each cgroup_subsys_state release Tejun Heo
2013-08-13 1:19 ` [PATCHSET cgroup/for-3.12] cgroup: decouple cgroup_subsys_state lifetime from that of cgroup Li Zefan
2013-08-13 15:02 ` Tejun Heo
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