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From:   Roman Gushchin <guro@fb.com>
To:     Christian Borntraeger <borntraeger@de.ibm.com>
CC:     "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "hannes@cmpxchg.org" <hannes@cmpxchg.org>,
        Kernel Team <Kernel-team@fb.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "longman@redhat.com" <longman@redhat.com>,
        "shakeelb@google.com" <shakeelb@google.com>,
        "vdavydov.dev@gmail.com" <vdavydov.dev@gmail.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: WARNING bisected (was Re: [PATCH v7 08/10] mm: rework non-root
 kmem_cache lifecycle management)
Thread-Topic: WARNING bisected (was Re: [PATCH v7 08/10] mm: rework non-root
 kmem_cache lifecycle management)
Thread-Index: AQHVoF1eUJGIXl/jo02oA2+fhmBRU6eV2PaAgAAAgACAAB16AIABbCgAgAIbagA=
Date:   Sun, 24 Nov 2019 00:39:30 +0000
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On Fri, Nov 22, 2019 at 05:28:46PM +0100, Christian Borntraeger wrote:
> On 21.11.19 19:45, Roman Gushchin wrote:
> > I see. Do you know, which kmem_cache it is? If not, can you, please,
> > figure it out?
>=20
> The release function for that ref is kmemcg_cache_shutdown.=20
>=20

Hi Christian!

Can you, please, test if the following patch resolves the problem?

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 8afa188f6e20..628e5f0ee19e 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -888,6 +888,8 @@ static int shutdown_memcg_caches(struct kmem_cache *s)
=20
 static void flush_memcg_workqueue(struct kmem_cache *s)
 {
+	bool wait_for_children;
+
 	spin_lock_irq(&memcg_kmem_wq_lock);
 	s->memcg_params.dying =3D true;
 	spin_unlock_irq(&memcg_kmem_wq_lock);
@@ -904,6 +906,13 @@ static void flush_memcg_workqueue(struct kmem_cache *s=
)
 	 * previous workitems on workqueue are processed.
 	 */
 	flush_workqueue(memcg_kmem_cache_wq);
+
+	mutex_lock(&slab_mutex);
+	wait_for_children =3D !list_empty(&s->memcg_params.children);
+	mutex_unlock(&slab_mutex);
+
+	if (wait_for_children)
+		rcu_barrier();
 }
 #else
 static inline int shutdown_memcg_caches(struct kmem_cache *s)

--

Thanks!