Wind River Support Network

Description

Prime team add cgroup-bring-back-kill_cnt-to-order-css-destruction.patch when they create ccm layer.
The reason why they add this patch is following.

"the workitem to offline parent can get run before workitem to offline child;
parent's mem_cgroup_reparent_charges() circles around waiting for the
child's pages to be reparented to its lrus, but it's holding cgroup_mutex
which prevents the child from reaching its mem_cgroup_reparent_charges().

Further testing showed that an ordered workqueue for cgroup_destroy_wq
is not always good enough: percpu_ref_kill_and_confirm's call_rcu_sched
stage on the way can mess up the order before reaching the workqueue.

Instead bring back v3.11's css kill_cnt, repurposing it to make sure
that offline_css() is not called for parent before it has been called
for all children."

I found that this patch was not merged into mainline when I was analyzing a issue about cgroup.
The reason, why mainline did not accept the patch, is in the following link.
https://lkml.org/lkml/2014/2/12/716

And then I found that there are two patches as below in mainline for solving the same problem.
cgroup-make-sure-a-parent-css-isn-t-freed-before-its-in-mainline.patch
cgroup-make-sure-a-parent-css-isn-t-offlined-before-in-mainline.patch

The role of the two patches are following.

"There are three subsystem callbacks in css shutdown path -
css_offline(), css_released() and css_free().  Except for
css_released(), cgroup core didn't use to guarantee the order of
invocation.  css_offline() or css_free() could be called on a parent
css before its children.  This behavior is unexpected and led to
use-after-free in cpu controller."

So I backported the two patches as below into ccm layer after I removed the cgroup-bring-back-kill_cnt-to-order-css-destruction.patch.
0001-cgroup-make-sure-a-parent-css-isn-t-freed-before-its.patch
0001-cgroup-make-sure-a-parent-css-isn-t-offlined-before-.patch

Please help to check if it should be merge into wrlinux7.

Other Downloads

• Wind River Linux 7.0.0.23
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• Wind River Linux 7.0.0.28
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• Wind River Linux 7.0.0.31