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SubjectRe: [PATCH 4/5] oom: the points calculation of child processes must use find_lock_task_mm() too
On 05/31, KOSAKI Motohiro wrote:
>
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -87,6 +87,7 @@ static struct task_struct *find_lock_task_mm(struct task_struct *p)
> unsigned long badness(struct task_struct *p, unsigned long uptime)
> {
> unsigned long points, cpu_time, run_time;
> + struct task_struct *c;
> struct task_struct *child;
> int oom_adj = p->signal->oom_adj;
> struct task_cputime task_time;
> @@ -124,11 +125,13 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
> * child is eating the vast majority of memory, adding only half
> * to the parents will make the child our kill candidate of choice.
> */
> - list_for_each_entry(child, &p->children, sibling) {
> - task_lock(child);
> - if (child->mm != p->mm && child->mm)
> - points += child->mm->total_vm/2 + 1;
> - task_unlock(child);
> + list_for_each_entry(c, &p->children, sibling) {
> + child = find_lock_task_mm(c);
> + if (child) {
> + if (child->mm != p->mm)
> + points += child->mm->total_vm/2 + 1;
> + task_unlock(child);
> + }

Acked-by: Oleg Nesterov <oleg@redhat.com>




And, I think we need another patch on top of this one. Note that
this list_for_each_entry(p->children) can only see the tasks forked
by p, it can't see other children forked by its sub-threads.

IOW, we need

do {
list_for_each_entry(c, &t->children, sibling) {
...
}
} while_each_thread(p, t);

Probably the same for oom_kill_process().

What do you think?

Oleg.



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