cgroup: make sure a parent css isn't freed before its children
[ Upstream commit 8bb5ef79bc
]
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>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
wifi-calibration
parent
3398611863
commit
cef12dbf18
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@ -4378,14 +4378,15 @@ static void css_free_work_fn(struct work_struct *work)
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if (ss) {
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/* css free path */
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struct cgroup_subsys_state *parent = css->parent;
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int id = css->id;
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if (css->parent)
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css_put(css->parent);
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ss->css_free(css);
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cgroup_idr_remove(&ss->css_idr, id);
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cgroup_put(cgrp);
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if (parent)
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css_put(parent);
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} else {
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/* cgroup free path */
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atomic_dec(&cgrp->root->nr_cgrps);
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