Sorry if this was already discussed, I have to admit that I ignored
the previous discussion ;) And it is possible I misread this patch
completely.
On 10/08, Chen Hanxiao wrote:
>
> This patch will show the hierarchy of pid namespace
> by /proc/pidns_hierarchy like:
>
> [root@localhost ~]#cat /proc/pidns_hierarchy
> /proc/18060/ns/pid /proc/18102/ns/pid /proc/1534/ns/pid
> /proc/18060/ns/pid /proc/18102/ns/pid /proc/1600/ns/pid
> /proc/1550/ns/pid
Well, personally I too think that the filenames look a bit strange,
can't it just print the numbers?
And, iiuc what this patch does... perhaps in this case we should
simply add "struct list_head children" into struct pid_namespace?
In this case the patch will be really simple. I dunno.
> +pidns_list_add(struct pid *pid, struct list_head *list_head,
> + struct pid_namespace *curr_ns)
> +{
> + struct pidns_list *ent;
> + struct pid_namespace *ns;
> +
> + if (is_child_reaper(pid)) {
> + ent = kmalloc(sizeof(*ent), GFP_KERNEL);
GFP_KERNEL under rcu_read_lock(). This is not safe without
CONFIG_PREEMPT_RCU.
> + if (!ent)
> + return -ENOMEM;
> +
> + ent->pid = pid;
> + ns = pid->numbers[pid->level].ns;
> + if (curr_ns) {
> + /* add pids who is the child of curr_ns */
> + for (; ns != NULL; ns = ns->parent)
> + if (ns == curr_ns)
> + list_add_tail(&ent->list, list_head);
afaics, it doesn't make sense to continue after list_add() ?
> +static int proc_pidns_list_refresh(struct pid_namespace *curr_ns)
> +{
> + struct pid *pid;
> + struct task_struct *p;
> + int rc;
> +
> + /* collect pid in differet ns */
> + for_each_process(p) {
Hmm. We only want the tasks from our namespace, yes? Perhaps find_ge_pid()
makes more sense?
> + pid = task_pid(p);
Well, in theory you need barrier() here. Or perhaps we should add
ACCESS_ONCE() into task_pid()...
And imho it would be better to declare pidns_list/pidns_tree locally
in nslist_proc_show() and pass them to the callees.
Oleg.
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