From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f71.google.com (mail-lf0-f71.google.com [209.85.215.71]) by kanga.kvack.org (Postfix) with ESMTP id 2EF556B0069 for ; Wed, 30 Nov 2016 21:25:04 -0500 (EST) Received: by mail-lf0-f71.google.com with SMTP id g12so49680589lfe.5 for ; Wed, 30 Nov 2016 18:25:04 -0800 (PST) Received: from mail.mimuw.edu.pl (mail.mimuw.edu.pl. [2001:6a0:5001::4]) by mx.google.com with ESMTPS id v67si33124782lfi.271.2016.11.30.18.25.02 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 30 Nov 2016 18:25:02 -0800 (PST) Date: Thu, 1 Dec 2016 03:24:54 +0100 From: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= Subject: Re: [Bug 189181] New: BUG: unable to handle kernel NULL pointer dereference in mem_cgroup_node_nr_lru_pages Message-ID: <20161201022454.GB21693@mail-personal> References: <20161129145654.c48bebbd684edcd6f64a03fe@linux-foundation.org> <20161130170040.GJ18432@dhcp22.suse.cz> <20161130181653.GA30558@cmpxchg.org> <20161130183016.GO18432@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ZfOjI3PrQbgiZnxM" Content-Disposition: inline In-Reply-To: <20161130183016.GO18432@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Johannes Weiner , Andrew Morton , Mel Gorman , bugzilla-daemon@bugzilla.kernel.org, linux-mm@kvack.org, Vladimir Davydov --ZfOjI3PrQbgiZnxM Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Nov 30, 2016 at 07:30:17PM +0100, Michal Hocko wrote: > On Wed 30-11-16 13:16:53, Johannes Weiner wrote: > > Hi Michael, > >=20 > > On Wed, Nov 30, 2016 at 06:00:40PM +0100, Michal Hocko wrote: > [...] > > > diff --git a/mm/workingset.c b/mm/workingset.c > > > index 617475f529f4..0f07522c5c0e 100644 > > > --- a/mm/workingset.c > > > +++ b/mm/workingset.c > > > @@ -348,7 +348,7 @@ static unsigned long count_shadow_nodes(struct sh= rinker *shrinker, > > > shadow_nodes =3D list_lru_shrink_count(&workingset_shadow_nodes, sc= ); > > > local_irq_enable(); > > > =20 > > > - if (memcg_kmem_enabled()) { > > > + if (memcg_kmem_enabled() && sc->memcg) { > > > pages =3D mem_cgroup_node_nr_lru_pages(sc->memcg, sc->nid, > > > LRU_ALL_FILE); > > > } else { > >=20 > > If we do that, I'd remove the racy memcg_kmem_enabled() check > > altogether and just check for whether we have a memcg or not. >=20 > But that would make this a memcg aware shrinker even when kmem is not > enabled... >=20 > But now that I am looking into the code > shrink_slab: > if (memcg_kmem_enabled() && > !!memcg !=3D !!(shrinker->flags & SHRINKER_MEMCG_AWARE)) > continue; >=20 > this should be taken care of already. So sc->memcg should be indeed > sufficient. So unless I am missing something I will respin my local > patch and post it later after the reporter has some time to test the > current one. The above patch seems to help. At least the problem haven't occurred for the last ~40 VM startups. > =20 > > What do you think, Vladimir? >=20 --=20 Pozdrawiam / Best Regards, Marek Marczykowski-G=C3=B3recki | RLU #390519 marmarek at staszic waw pl | xmpp:marmarek at staszic waw pl --ZfOjI3PrQbgiZnxM Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlg/ifYACgkQXmmj5DNap+pIDACg2IMLGxsQKOObDnHM9yFNMoF+ XkoAn3m8KbgSIyzTTbs68+p+eMnR40x7 =EAZK -----END PGP SIGNATURE----- --ZfOjI3PrQbgiZnxM-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org