On Sun, Sep 03, 2023 at 02:27:56PM +0000, Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
> static inline bool task_under_cgroup_hierarchy(struct task_struct *task,
> struct cgroup *ancestor)
> {
> struct css_set *cset = task_css_set(task);
> + struct cgroup *cgrp;
> + bool ret = false;
> + int ssid;
> +
> + if (ancestor->root == &cgrp_dfl_root)
> + return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
> +
> + for (ssid = 0; ssid < CGROUP_SUBSYS_COUNT; ssid++) {
This loop were better an iteration over cset->cgrp_links to handle any
v1 hierarchy (under css_set_lock :-/).
> + if (!ancestor->subsys[ssid])
> + continue;
>
> - return cgroup_is_descendant(cset->dfl_cgrp, ancestor);
> + cgrp = task_css(task, ssid)->cgroup;
Does this pass on a lockdep-enabled kernel?
See conditions in task_css_set_check(), it seems at least RCU read lock
would be needed (if not going through cgrp_links mentioned above).
HTH,
Michal
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