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| author | Tejun Heo <tj@kernel.org> | 2016-01-21 15:32:15 -0500 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2016-01-22 10:42:58 -0500 |
| commit | 8bb5ef79bc0f4016ecf79e8dce6096a3c63603e4 (patch) | |
| tree | 3a2129fd05443c134b033fd476f93ca0faf28b01 /kernel/cgroup.c | |
| parent | aa226ff4a1ce79f229c6b7a4c0a14e17fececd01 (diff) | |
| download | lwn-8bb5ef79bc0f4016ecf79e8dce6096a3c63603e4.tar.gz lwn-8bb5ef79bc0f4016ecf79e8dce6096a3c63603e4.zip | |
cgroup: make sure a parent css isn't freed before its children
There are three subsystem callbacks in css shutdown path -
css_offline(), css_released() and css_free(). Except for
css_released(), cgroup core didn't 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 bugs in cpu and
memory controller.
The previous patch updated ordering for css_offline() which fixes the
cpu controller issue. While there currently isn't a known bug caused
by misordering of css_free() invocations, let's fix it too for
consistency.
css_free() ordering can be trivially fixed by moving putting of the
parent css below css_free() invocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index d01587793865..d27904c193da 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4657,14 +4657,15 @@ static void css_free_work_fn(struct work_struct *work) if (ss) { /* css free path */ + struct cgroup_subsys_state *parent = css->parent; int id = css->id; - if (css->parent) - css_put(css->parent); - ss->css_free(css); cgroup_idr_remove(&ss->css_idr, id); cgroup_put(cgrp); + + if (parent) + css_put(parent); } else { /* cgroup free path */ atomic_dec(&cgrp->root->nr_cgrps); |