Re: [PATCH 0/2] memcg: mm_update_next_owner() should skip kthreads

[Michal Hocko]

On Fri 18-04-14 20:44:41, Oleg Nesterov wrote:
> On 04/18, Michal Hocko wrote:
> >
> > On Fri 18-04-14 19:26:31, Oleg Nesterov wrote:
> > > On 04/18, Oleg Nesterov wrote:
> > > >
> > > > Hmm. I seem to see a bug in this function, it can be fulled by use_mm,
> > > > but I am not sure this can explain the problem. I'll send a patch.
> > >
> > > Untested, please review. But it really looks "obviously wrong", and note
> > > that unuse_mm() doesn't do mm_update_next_owner(). (just in case, do not
> > > confuse it with unuse_mm() in mm/swapfile.c).
> >
> > Both patches seem to be correct but I am missinng why they are marked as
> > memcg: when they are touching generic mm_update_next_owner path.
> 
> Well, this is because I didn't know which prefix should I use. I looked
> at git-blame to see who changed this function, picked the random 733eda7ac
> "memcg: clear mm->owner when last possible owner leaves" commit and copied
> "memcg" from there.
> 
> OTOH, mm->owner is used by mm/memcontrol.c, so perhaps the prefix is fine?

OK, I didn't realize memcg is the only user.

> I do not even understand why do we have CONFIG_MM_OWNER, perhaps it should
> die?

I have to dig into history to check why it has been introduced in the
first place. It might be possible it is not relevant anymore.
-- 
Michal Hocko
SUSE Labs
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