On Tue, 30 Mar 2010, anfei wrote:
> > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > index afeab2a..9aae208 100644
> > > --- a/mm/oom_kill.c
> > > +++ b/mm/oom_kill.c
> > > @@ -588,12 +588,8 @@ retry:
> > > if (PTR_ERR(p) == -1UL)
> > > return;
> > >
> > > - /* Found nothing?!?! Either we hang forever, or we panic. */
> > > - if (!p) {
> > > - read_unlock(&tasklist_lock);
> > > - dump_header(NULL, gfp_mask, order, NULL);
> > > - panic("Out of memory and no killable processes...\n");
> > > - }
> > > + if (!p)
> > > + p = current;
> > >
> > > if (oom_kill_process(p, gfp_mask, order, points, NULL,
> > > "Out of memory"))
> >
> > The reason p wasn't selected is because it fails to meet the criteria for
> > candidacy in select_bad_process(), not necessarily because of a race with
> > the !p->mm check that the -mm patch cited above fixes. It's quite
> > possible that current has an oom_adj value of OOM_DISABLE, for example,
> > where this would be wrong.
>
> I see. And what about changing mem_cgroup_out_of_memory() too?
>
The memory controller is different because it must kill a task even if
another task is exiting since the imposed limit has been reached.
> 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?
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