The commit is pushed to "branch-rh7-3.10.0-229.7.2-ovz" and will appear at
https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.6.3
------>
commit ce835adec25190f76a26cc97f1a38aadc93a4957
Author: Vladimir Davydov <vdavy...@parallels.com>
Date: Fri Aug 28 14:49:25 2015 +0400
ms/cgroup: reorder the operations in cgroup_destroy_locked()
Patchset description:
Pulling upstream patches converting css refcnt to percpu_ref.
https://jira.sw.ru/browse/PSBM-34174
Kent Overstreet (2):
percpu: implement generic percpu refcounting
percpu-refcount: Don't use silly cmpxchg()
Tejun Heo (9):
percpu-refcount: consistently use plain (non-sched) RCU
percpu-refcount: cosmetic updates
percpu-refcount: add __must_check to percpu_ref_init() and don't use
ACCESS_ONCE() in percpu_ref_kill_rcu()
percpu-refcount: implement percpu_ref_cancel_init()
percpu-refcount: implement percpu_tryget() along with
percpu_ref_kill_and_confirm()
percpu-refcount: use RCU-sched insted of normal RCU
cgroup: reorder the operations in cgroup_destroy_locked()
cgroup: split cgroup destruction into two steps
cgroup: use percpu refcnt for cgroup_subsys_states
===
This patch description:
From: Tejun Heo <t...@kernel.org>
This patch reorders the operations in cgroup_destroy_locked() such
that the userland visible parts happen before css offlining and
removal from the ->sibling list. This will be used to make css use
percpu refcnt.
While at it, split out CGRP_DEAD related comment from the refcnt
deactivation one and correct / clarify how different guarantees are
met.
While this patch changes the specific order of operations, it
shouldn't cause any noticeable behavior difference.
Signed-off-by: Tejun Heo <t...@kernel.org>
Acked-by: Li Zefan <lize...@huawei.com>
(cherry picked from commit 455050d23e1bfc47ca98e943ad5b2f3a9bbe45fb)
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
Conflicts:
kernel/cgroup.c
---
kernel/cgroup.c | 48 ++++++++++++++++++++++++++----------------------
1 file changed, 26 insertions(+), 22 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b073fba..062e0f4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4367,9 +4367,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
/*
* Block new css_tryget() by deactivating refcnt and mark @cgrp
- * removed. This makes future css_tryget() and child creation
- * attempts fail thus maintaining the removal conditions verified
- * above.
+ * removed. This makes future css_tryget() attempts fail which we
+ * guarantee to ->css_offline() callbacks.
*/
for_each_subsys(cgrp->root, ss) {
struct cgroup_subsys_state *css = cgrp->subsys[ss->subsys_id];
@@ -4379,6 +4378,30 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
}
set_bit(CGRP_REMOVED, &cgrp->flags);
+ raw_spin_lock(&release_list_lock);
+ if (!list_empty(&cgrp->release_list))
+ list_del_init(&cgrp->release_list);
+ raw_spin_unlock(&release_list_lock);
+
+ /*
+ * Remove @cgrp directory. The removal puts the base ref but we
+ * aren't quite done with @cgrp yet, so hold onto it.
+ */
+ dget(d);
+ cgroup_d_remove_dir(d);
+
+ /*
+ * Unregister events and notify userspace.
+ * Notify userspace about cgroup removing only after rmdir of cgroup
+ * directory to avoid race between userspace and kernelspace.
+ */
+ spin_lock(&cgrp->event_list_lock);
+ list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
+ list_del_init(&event->list);
+ schedule_work(&event->remove);
+ }
+ spin_unlock(&cgrp->event_list_lock);
+
/* tell subsystems to initate destruction */
for_each_subsys(cgrp->root, ss)
offline_css(ss, cgrp);
@@ -4393,34 +4416,15 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
for_each_subsys(cgrp->root, ss)
css_put(cgrp->subsys[ss->subsys_id]);
- raw_spin_lock(&release_list_lock);
- if (!list_empty(&cgrp->release_list))
- list_del_init(&cgrp->release_list);
- raw_spin_unlock(&release_list_lock);
-
/* delete this cgroup from parent->children */
list_del_rcu(&cgrp->sibling);
list_del_init(&cgrp->allcg_node);
- dget(d);
- cgroup_d_remove_dir(d);
dput(d);
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
- /*
- * Unregister events and notify userspace.
- * Notify userspace about cgroup removing only after rmdir of cgroup
- * directory to avoid race between userspace and kernelspace.
- */
- spin_lock(&cgrp->event_list_lock);
- list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
- list_del_init(&event->list);
- schedule_work(&event->remove);
- }
- spin_unlock(&cgrp->event_list_lock);
-
return 0;
}
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