Re: [PATCH 3/9] oom: oom_kill_process() doesn't select kthread child

KOSAKI Motohiro
2010-06-17T01:51:53Z

> On Wed, Jun 16, 2010 at 08:32:08PM +0900, KOSAKI Motohiro wrote:
> > Now, select_bad_process() have PF_KTHREAD check, but oom_kill_process
> > doesn't. It mean oom_kill_process() may choose wrong task, especially,
> > when the child are using use_mm().
> Now oom_kill_process is called by three place.
>
> 1. mem_cgroup_out_of_memory
> 2. out_of_memory with sysctl_oom_kill_allocating_task
> 3. out_of_memory with non-sysctl_oom_kill_allocating_task
>
> I think it's no problem in 1 and 3 since select_bad_process already checks
> PF_KTHREAD. The problem in in 2.
> So How about put the check before calling oom_kill_process in case of
> sysctl_oom_kill_allocating task?
>
> if (sysctl_oom_kill_allocating_task) {
> if (!current->flags & PF_KTHREAD)
> oom_kill_process();
>
> It can remove duplicated PF_KTHREAD check in select_bad_process and
> oom_kill_process.

This patch changed child selection logic. select_bad_process() doesn't
check victim's child. IOW, this is necessary when all 1-3.