On Tue, 30 Mar 2010 23:07:08 -0700 (PDT)
David Rientjes <rientjes@xxxxxxxxxx> wrote:
> On Wed, 31 Mar 2010, KAMEZAWA Hiroyuki wrote:
>
> > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > > index 0cb1ca4..9e89a29 100644
> > > > --- a/mm/oom_kill.c
> > > > +++ b/mm/oom_kill.c
> > > > @@ -510,8 +510,10 @@ retry:
> > > > if (PTR_ERR(p) == -1UL)
> > > > goto out;
> > > >
> > > > - if (!p)
> > > > - p = current;
> > > > + if (!p) {
> > > > + read_unlock(&tasklist_lock);
> > > > + panic("Out of memory and no killable processes...\n");
> > > > + }
> > > >
> > > > if (oom_kill_process(p, gfp_mask, 0, points, limit, mem,
> > > > "Memory cgroup out of memory"))
> > > >
> > >
> > > This actually does appear to be necessary but for a different reason: if
> > > current is unkillable because it has OOM_DISABLE, for example, then
> > > oom_kill_process() will repeatedly fail and mem_cgroup_out_of_memory()
> > > will infinitely loop.
> > >
> > > Kame-san?
> > >
> >
> > When a memcg goes into OOM and it only has unkillable processes (OOM_DISABLE),
> > we can do nothing. (we can't panic because container's death != system death.)
> >
> > Because memcg itself has mutex+waitqueue for mutual execusion of OOM killer,
> > I think infinite-loop will not be critical probelm for the whole system.
> >
> > And, now, memcg has oom-kill-disable + oom-kill-notifier features.
> > So, If a memcg goes into OOM and there is no killable process, but oom-kill is
> > not disabled by memcg.....it means system admin's mis-configuraton.
> >
> > He can stop inifite loop by hand, anyway.
> > # echo 1 > ..../group_A/memory.oom_control
> >
>
> Then we should be able to do this since current is by definition
> unkillable since it was not found in select_bad_process(), right?
To me, this patch is acceptable and seems reasnoable.
But I didn't joined to memcg development when this check was added
and don't know why kill current..
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c7ba5c9e8176704bfac0729875fa62798037584d
Addinc Balbir to CC. Maybe situation is changed now.
Because we can stop inifinite loop (by hand) and there is no rushing oom-kill
callers, this change is acceptable.
Thanks,
-Kame
> ---
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -500,12 +500,9 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
> read_lock(&tasklist_lock);
> retry:
> p = select_bad_process(&points, limit, mem, CONSTRAINT_NONE, NULL);
> - if (PTR_ERR(p) == -1UL)
> + if (!p || PTR_ERR(p) == -1UL)
> goto out;
>
> - if (!p)
> - p = current;
> -
> if (oom_kill_process(p, gfp_mask, 0, points, limit, mem,
> "Memory cgroup out of memory"))
> goto retry;
>
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